Hey fishy! Nice game name! If I was you I would first figure out, game mechanics, the style of game you want, storyline, and 'do I want it to be 2d or 3d?' If you want it 2d figure out if you want it 16 bit 32 bit etc or just smooth hd graphics! If you want it to be pixel graphics you could try and teach yourself how to draw pixel art! (Or commission me lol!) There are a lot of game making apps out there like unity for instance!
unity can make 2d and 3d games so it's a great application! Unity also has assets, like tilests and 3d packages!! Don't forget to keep us updated on your progress!!