The best occupation would be being a runesmith considering not only him being an artificial intelligence made of different code and programming, Euclid would have incredible potential in the field of runes, but runes are also a possible route to control magic and Mana after all runes are instructions to tell mana how to effect reality, and if he can use runes to control the world around him then he could be just fine except for the fact that to usual create or start a rune you need mana and Euclid doesn't posses any mana storage or way to control mana.
'Though if I somehow engrave some kind of absorption runes on the nanites then I can also do projection like a controlled Mana Lazer, which will allow me to engrave runes easily in most cases and sense my runes are all in state of quantum entanglement and are all linked it would be easy to move mana from one nanite to another and I may even be able to use magic then, as I wouldn't need a Mana storage like any other creature; because as my nanites start to absorb more mana they'll become attuned to Mana like some metal being attuned like steel to Mana steel which is used by blacksmiths. Alright that's one occupation my next one will be artifact crafting.'
Artifact crafting is a mix of blacksmithing or creating of some kind alongside runes to create an object that contains incredible power, whether it's a necklace that dominates a persons mind apon them wearing it, a sword that has the power use Mana to reinforce or amplify the swords own abilities, or any other magic technology, which also included automatons; though Euclid already had an understanding of advanced robotics it couldn't hurt to learn more as he could learn how to improve himself more.
'As the people of this world and tower have been using magic since their species has been around, that's what has been their focus, magic and Mana, except for those subject the world has completely forgotten to understand the rest of the world and thus have a very little understanding of the science and technology, if I were to combine the knowledge of magic and Mana that I'll learn in the future with the understanding of not only humans, but the advanced knowledge that I had progressed that had passed the humans old information then I'll create the perfect fusion of science, technology, and magic. Now the last occupation will be alchemy'
In the human world alchemy was the medieval forerunner of chemistry, based on the supposed transformation of matter. It was concerned particularly with attempts to convert base metals into gold or to find a universal elixir. But here alchemy is a branch of magic that involves the transformation of matter, usually by combining different substances or using special tools. Alchemists can create potions, elixirs, metals, and other products with various effects. It's more of a magical chemistry, and with Euclids advanced understanding of math, physics, and chemistry it would be very useful to further his own knowledge and would be quite easy with his understanding, and theoretical knowledge.
'Not to mention that not only could alchemy be useful in some aspects, its one, if not the most locative business and trade in the entire tower, with all health, stamina, and Mana potions being some of the most bought items in the tower, not to mention elixirs to help improve mana quality and quantitie, increase your strength and even bring back the dead though that last one may be impossible as it's just a myth, but regardless whether or not it is fact or fiction, the alchemy business is where most of the towers money is as well as where powerful individuals gather, after all who doesn't want to be a potential friend with a powerful alchemist; as the possible benefits that one could gain could save your life if your friends with the right people. In fact it's pretty much the same for all high-level occupations to a lesser degree, as long as your talented enough in that field then money, people and resources will come to you eventually, and I definitely need money right now so all these fields will help with that'
Now that Euclid has decided the occupations he will go into he has to learn about the rudimentary or basics of each field, as before going to the guild to take the test for that specific field he has to gain knowledge of that field then take a test that's examines his knowledge of that field, if he succeeds then he will be given some resources and more information on the topic; which will help him progress in that field going forward.
Walking out of the job section, Euclid got a weird look form the old man one last time before hearing the man mumbling to himself about kids being more and more pretentious these days before going back to his book.
As Euclid walked out of the section for jobs he went over his available knowledge of where the section on runes, artifact crafting, and alchemy were located but found no sections for any of those specific topics, their was a section for all the advanced occupations together that held some rudimentary information on those topics, but not a enough for Euclid to be content.
Only the books available for runes was 'what are runes and their uses', 'the components of a rune' , quickly scanning through the books, he memorized the information leaning that runes are like parts of a circuit, one rune is where Mana is contained or injected, if the goal is to create fire, that mana will follow a line connected to another rune which will produce a spark with the Mana, while also using the Mana as fuel to successfully create fire, but unlike a electric circuits that are 3 dimension runes are 2 dimensions, they also don't have a limit on shrinking.
'Not to mention that from the little that I've read about Mana; it also doesn't experience time like photons and tachyons and also phase through objects like neutrinos, while having little to no impact on the surroundings usually unless directly absorbed or it's a rare circumstance, which means the speed for a rune to activate is instantaneous.'
While learning about runes, Euclid figured out that a group of runes is called a formations, while a group of formations is called an array. Runes are used in buildings, magic, weapons, artifacts, medicine, healing, even body strengthening, he also learned how they were drawn and the materials needed, as well as the basic symbols which was a lot of geometry, attempts at chemistry or alchemy in this case and instead of electrical engineering it was more Mana circuit engineering.
'Now that I got a bare basic understanding of runes; I should look at the other books for artifact crafting and alchemy but I should first ask the librarian if there are other books in the library for these topics, as it doesn't make much sense for a library like this; to have this little information on subjects'
Walking around shelves of books he started walking towards the librarian before reaching the desk and knocking on it.
"Excuse me miss librarian, do you happen to know where there might be more books on specific occupation subjects as there seemed to be very little information?"
As Euclid asked the question, the librarian glanced at him before she seemed to sigh before turning giving him a quick answer before going back to her own business
"Ah you, don't you know that the guilds have control over their respective knowledge, why would that information be here."
"Ah that makes sense, thank you for your time again."
As she turned back to her own business, Euclid understood everything, if every guild had near complete control over their respective knowledge than they can control more people in their particular field, after all where else are they going to get more information, each of these guilds is like a monarch and has complete control on the their entire specific industry; while also having a monopoly on their knowledge, you'll eventually have to go to the guild in your profession to get more information if you don't want to spend all your time doing your own research.
Now understanding the reason for the lack of books on certain topics, Euclid started heading back to the section he was currently in before picking up a book about artifact crafting.
As it turned out, artifact crafting involved lots of runes, enchantment; which is another field related to rune but slightly different, it also involved blacksmithing and other fields.
All in all, artifact creation was the creation of a tool with a magical or unique property, like a pair of boots that allow flight would be an artifact.
'Technically, I would be an artifact considering I was a tool created with the unique property of intelligence, but just happened to gain sentience, but it seems like I'm a also not unique in this circumstance; as often enough a high level artifacts may give birth to something called an artifact spirit, which is a consciousness developed by the artifact though artifact spirits seem to be different from regular spirits that are born from nature like earth spirits or others born when a natural element interacts with Mana for an extended period of time. Though I don't think artifact spirit would be the correct term in this world, more like artificial artifact spirit considering humans were trying to create an artificial consciousness, which would be an artifact with the properties of intelligence, so in this world I would be a mix between artificial spirit and artifact spirit making me a artificial artifact spirit... ahh don't go down this rabbit hole right now Euclid... Anyways, now I'm done with artifact crafting for now, I'll now move on to alchemy.'
Picking up Another couple o books about alchemy he started to memorize what the alchemy practice was. Alchemy was pretty much a person creating fire using magic to melt different components down to best forms and uses, since Mana seems to have in impact in living creature DNA, both plants and animals, as well as molecular compounds and increase the quality of the chemical make up, when people combine different chemicals from minerals, plants, and Mana the product created would be much more superior and magical.
Although alchemy sounds like the easiest profession, it requires math, a crude understanding of chemistry, a good memory of different animal, plants, and minerals, along with being able to follow a formula very closely and precisely, and alchemy takes a lot of time from a couple minutes to days, and the final outcome could be a terrible waste of resources as the concoction could completely fail costing a lot of money.
These are some of the reasons that make alchemy so hard and tiring, with most alchemist eventually quiting from stress or possibly become bankrupt. But to most, the possible rewards waiting for those who succeed in becoming a alchemist is worth the chance of failing and falling further than they started before.
'Now that I got a rudimentary idea of these fields I can go to one of the guilds to take the test, which will probably be the guild of runes first, then after I gain the needed knowledge for runes, I can start my own research later on, but after I'm done gaining the guilds knowledge I should go to find a trainer to train me in combat, then I'll start the 1st floor of the tower and see how that goes before going forward'
Deciding his future plans, Euclid walked out of the special occupations section and walked by the librarian, waving before walking out of the library.
Looking around, he remembered the map he had memorized before walking on the same main road just further down the street from the library, after a minute of walking he had spotted both the guild of runes and the guild of alchemy, but decided to stick with his plan for now while taking and passing the test of knowledge and get his rune guild card.
Walking up to the giant building that appeared to be around 5 stories tall he pushed the front door open and walked in, as soon as he walked in he noticed the men's immense amount of people, there was also a counter that had 4 receptionists, a board with a bunch of papers that appeared to be commissions, possible jobs, etc for runesmiths.
As of right now there weren't much people at the receptionists so he decided to walk up to one of them and finally begin his test.
"Hello miss, I would like to take the test to become a runesmiths do you know how I would go about doing that?"