I updated the rules because someone mentioned they were confusing;
1 - Only use you're own content unless you have both the permission of and give credit to the owner.
2 - No cheating and buying complete packs from the asset store and the such. You can download free assets but save your money and your sanity and don't purchase complete packs.
3 - Have fun. Don't stress it too much, game development is supposed to be as fun as the game's you are making.