C was my first ever programming language, and the only thing I can say about it is to always look out for resources you malloced.
Also pointers. definitely pointers. try to get a good grasp of double pointers and how they are used inside structs.
You may also want to implement the following algorithms/data structures so you have at least a good understanding on how usually pointers are used.
1. for each loop
2. stacks
3. lists
4. BST
on modern programming languages, these are simple. But on C, you need a good pointer knowledge to be able to create these