I am also learning C so I will point you to what I use. Please note I have stoped learning C so someone may have better resources than mine.
Editor: Notepad++
I like the syntax highlighting aspect and it is well supported so others can help you.
Compiler: The 84+CE Toolchain
I am not sure if you are learning C to program the 84+CE with, or for PC, but I use the C toolchain. For PC, C compiling, I will leave that for others to suggest. The C tools (for the 84PCE), can be fou d
here. You need to install the toolchain on PC, and send the clibs to the calc (or CEmu). Follow the docs for more info.
Tutorial: learn-c
I found
this free website to be useful for me. I did not spend alot of time on C, but I used this site and it helped me. It has a compiler to test code as well
Hope this helps and good luck!