I just buy as I go along.

I've only bought 2 pairs of maternity pants and one skirt.

All my regular tops still fit. Otherwise I just buy cheap and cute tops from Cotton On in the next size up. Also all my skirts with elastic waists still fit. So these are good for work. Should be fine for a bit longer as it's still warm here.

And my underwear still fits. As for bras I never wore underwire ones so I haven't had to change. I've always worn crop top styles like the ones by "Ambra Body Soft".

So I'm doing well!!!