This is very personal and I can just say what I use. It also depend on how much money you want to spend. A fast Amiga, with much RAM, HD and gfx-card is of course very nice. I noticed that the compile-time decreased a lot when I bought my A4000, compared to a A3000.

I have always used SAS/C compiler, the last version is 6.58. SAS/C don't support Amiga any more but Steve Krueger still do updates for SAS/C. He is even working on a PPC-version.

SAS/C is very stable and has been developed during long time, and can be bought very cheap today. There are others like StormC from Haage&Partner. It's a rather new compiler with better GUI and C++ support than SAS/C. I have heard both good and bad on this package. V3.0 is now released

The editor is another personal choice. I have always used CygnusEd. But there are others like GoldEd, FrexxEd, BlacksEditor etc. Another handy tool is CHelp. It's a commodity that wait for commands from Ced to look up things in the AutoDoc and includefiles. It's so simple, you just place the cursor over a keyword or function and press a F-key and you have the doc in a window.You can't remember all arguments and structures and it's much quicker to use the computer than a book.

You need documentation if you want to use Intuition, graphic, sound or whatever.The developer CD is a nice beginning but a books are also good. Unfortunately there are only official docs for 2.0. It's RKRM Libraries, RKRM Devices and RKRM User Interfaces style guide. Go for Libraries if you want someone.