I'm not a great clothes modeller, and that isn't false modesty; every step I make just serves to illuminate another twist in the path. :) The first things I put up for download were props, textures for other people's stuff, and a morph. Add-ons like this are a good place to start, I suggest. After that, the first few clothing items I distributed were based on other clothes, either those that came with Poser 4 or free downloads. That had the advantages of simplifying the modelling, and presenting a solid base to build the rigging on top of.