Im in the same boat. I am a single developer with no real experience. The trick I use is to find free or cheap assets on itch. You can find really cool assets on itch under the browse tab. As for music, there are some really good free (or cheap) musicians. I really like this guys music and I used this is the music I used for my game. For SFX, you can either find packs on itch or free ones on Pixabay. I recommend using these instead of AI because most game jams ban generative AI, and this supports indie artists. Even for AI, the best tool I recommend for it is Bezi as it is Claude, but with the power to see your game.