All the advice already here is very good and implementable. Here are my two cents. I have been programming in C professionally for the past 12 years, and I t

All the advice already here is very good and implementable. Here are my two cents. I have been programming in C professionally for the past 12 years, and I think the way to go would be to go implement a well known tool in C and then compare your code with the open source code of that tool. e.g. Git. You will learn a lot from how the feature that you chose to implement in a certain way was implemented in a completely different way for various reasons.