Hi!!
- Start with something very very easy. A tiny idea with some interactivity. Not necessary to be awesome, only something playable.
- Think about what your strengths and weaknesses are. At the begining, use your strengths to make something interesting. Later on, with more gamejams, try to explore your weakness and view how to improve these parts.
- Use a motor you control. If not, there are some tiny little programs to make simple games in itch.io to start (maybe this: https://the-l0bster.itch.io/pocket-platformer). Also narrative games (Bitsy, Twine, Ren’Py…). I use GDevelop because I know only a little of programming. But, in order to use to make a couple of cool prototypes, it was necessary to see a loooot of videos and tutorials (and sometimes is frustrating not to get what you want hehehe). Other with no code experience is Game Maker, for example.
- Think about the theme of a jam. Try to search something that you might like to explore.
- Your games will be played only a few times. Don´t worry about that. The main goal is to learn and to make something truly yours.