I made this game for a game jam, so I rushed to finish this game. It took about 1.5 days for me to finish, because I joined late.
For someone's first game, I think a small platformer wouldn't be too difficult, especially with all the tutorials that exist. I'd recommend finding a tutorial for whatever type of game you want to make, following that tutorial, and then adding your own ideas on top of that once you've finished the tutorial.
For example in this game, I built upon a basic platformer tutorial (you can see my first attempt at a platformer here). I optimized the code, added enemy/npc interactions, created the typewriter-like text, and added lighting effects. Future games I make will be able to use these features as well, now that I've done it once.
The most important part is finishing something. I've tried making many games in the past but never ended up finishing anything until I decided to create something for a game jam.