Well you can always find tutorial on YouTube but here are my tips after making games for all those years.
- Learn when to use code in Update and FixedUpdate. Update happens every frame. I mostly use it to handle inputs since it runs every frame. Try not to use it quite often. Fixed update runs 30 times in a second by default. This is the one I use to handle gradual decrease of player health or increase in climax bar.
- State machines and C# Events. Something I learned seeing an actual programmer looking into code of a quite popular game in the past. It may be difficult to understand at first but once you understand how things works, it makes life easier.
- Loading things from Resources, using loops. I only use two loops the most, for and foreach one.
- Using Invoke and Coroutines to run a code in time. They can be helpful when you want to stop something from running any further if a condition is met. Good example of this is sometimes moaning sounds stop when Masuo is talking with someone during sex.
- Learn a bit more about UI layout elements. This one come later when you want to add UI to the game.