Maternity Clothes Question

snuz81

This is my first pregnancy and I'll be 10 wks along tomorrow .  I'm not showing yet (bloated for sure, but definitely not showing), and was wondering when to start buying maternity clothes.  I feel like it's probably best to get a little here and there along the way, but I don't even know where to start!  When did/will y'all start getting clothes?

And I know this is probably a stupid question, but how does the sizing work?  Do you buy clothes for what size you normally wear, and they'll work for you throughout your pregnancy?