I bought a few things at a time as my regular clothes got uncomfortable. First to go was buying a bigger bra, and then some pants with the soft, elastic band at the top instead of the tight waistband. I think I got the bigger bra pretty early, and the pants in the 14th week or so.
I got my jeans from Motherhood. Some other pants at Old navy. And then I think almost all of my shirts are from JCPenny. They were much cheaper there then any where else for my tops.I think I have 1 or 2 from Target to. But I can wear jeans & t-shirts to work every day so its not to bad.
Good luck with your shopping!
I started wearing my first lot of maternity clothes at about 14 weeks, be proud of our bump and show it off when you can