After much Thought, I choose...
Tossing away option Five, I was only left with Geo-Spike, Geo-Bullet, Geo-Wall, and Geo-Skin. After some careful consideration, although a cool gimmick, I also ignored the Geo-Wall skill, leaving only Spike, Bullet, and Skin.
Each of these three could potentially be extremely useful in a fight or even daily life. I, of course, wasn't above ruling out using skills to make my quality of life slightly better, even though I tossed out the two that I could use to build a LITERAL fortress for a home.
The two didn't vibe with me, as the only conceivable way I could use them was to either wall myself up like a turtle or hide away; and considering if classes were a thing, I would be regarded as an assassin, neither choice was fitting.