Regardless where you get them (Murray's is preferred) they are not going to be presentable until they've been washed a few dozen times. Soaked in salt water and dried in the sun is even better, but that takes longer.
CMDC is exactly right - khakis and a white or blue shirt. Campaign staff are expected to look exhausted and rumpled. Keep a blazer around for events.
If you decide to buy a suit, try to find one with two pair of pants - you'll be spending a lot of time on your knees.