Black maternity tees are a great and very useful basic (white tees weren't as good because my black bella band showed through). (corporettemoms.com)
Another small, yet worthwhile investment is a bella band... it is well worth the money to keep your scrubs up without having to tie them above your expanding belly. (mothersinmedicine.com)
I got two bella bands — one in black and one in grey, so I could expand my pants for the first 5 months. (corporettemoms.com)