I had a brilliant idea while standing in the middle of store. I made a beeline for the back of the store to the clearance section and searched for shirts made of stretchy material a few sizes larger than what I would normally wear (to accommodate a growing belly). I was able to find 4 tank tops for about $2 each after my 10% off coupon! I'm still wearing them now at 34 weeks pregnant and they have turned out to be an awesome buy.
Pants are a bit trickier but anything stretchy and low rise (so your belly can grow) works pretty good too. You may have to get something in a size or two larger to fit the best and the longest during your pregnancy.