Well, it could be amazing. You might wish for powerful jutsu right from the start. For example, you could wish for the Sharingan to be able to compete with the strong characters in the Naruto world. Then you could use it to quickly learn new techniques and become a respected ninja.
Often in such fanfictions, there will be an antagonist as well. This could be a power - hungry entity in the twilight world who doesn't want the main character to succeed in using their wishes for good. The main character could be a person with a kind heart who is trying to bring positive change to the twilight realm. There might also be some side characters, like the main character's friends from their past life who are somehow connected to the new world and play important roles in the story.
The plot involves Rimuru's journey from being a rather weak (initially) slime to becoming a very powerful being. He meets many interesting characters. For example, there are the goblins he befriends early on. Rimuru helps them improve their living conditions. As the story progresses, he also has to deal with the threat of other more powerful monsters and even some human kingdoms that view his growing power with suspicion. In general, it's a story full of adventure, growth, and the forging of relationships in a magical and dangerous world.
To survive the first season in 'Reborn in Game of Thrones with Wishes', one must first use wishes wisely. For example, wishing for a basic understanding of the political situation in Westeros could be crucial. Also, try to make allies early on. Maybe wish for some kind of special skill that can impress the right people, like being an excellent healer. Avoid getting involved in the major power struggles too soon, as a newcomer is likely to be crushed. Instead, observe and learn from the sidelines.