There are issues with MACs. You can do a search on that word and do some reading with regard to problems others have had.
Generally you need the soundcard to have a line-in and a line-out available. A mic-in won't suffice. Those with laptops usually purchase an external USB soundcard.
As far as microphones are concerned. We recommend the Behringer ECM8000 because it's a relatively inexpensive omni directional flat microphone that we have the calibration file for on our download page. If you have a microphone that you feel is flat from ~15Hz to the upper frequency you're interested in, then it will be fine. Most microphones require a preamplifier to boost the signal to the line level for the soundcard.
You'll first need to calibrate your soundcard to create the file that compensates for its response inadequacies. See if you can get that done, because without it, you probably shouldn't go any further.
Read the
REW HELP files for info on performing the soundcard cal.....
brucek