The most important thing to do is get a really good compressor, with air filters and a built in or external regulator. This will keep your air tools from crapping out on you from too much PSI and dirty air.
For air tools, get what you need at harbor frieght. I have had mine for a while now, and they last a long time. The important thing to do is to oil your air tools once a day for every day you use them. That will prolong their life.
Don't get the bottom of the line impact gun or ratchet, get a couple steps up. It will increase the effeciency of the air that it uses, so you won't be running your compressor as much.
Scott