If you want to learn C, I would just take a text editor and a command line compiler. You can use GCC, or download free C/C++ compiler from Microsoft. Write small examples which cover the aspects you want to learn. I don't think a debugger will help here, but it might be nice to be able to look at expanded macros (which can be done by using --save-temps with GCC and watching the .i file). This is because most newbies misunderstand macros.
I would spend couple weeks writing small test programs and watching how they work. Most of things in C are straightforward. But you need to take some time to understand concepts. For example integer promotion is often neglected, but it means a lot, especially for small MCUs where C uses 16-bit integers. Other things which newbies have problems with are logic vs bitwise operations, understanding scope and duration, understanding sequence points, using pointers, understanding how structs are packed. IMHO, it is important to get a good grasp on basic concepts from the onset.