Progressing

I'm finally feeling like I'm starting to get somewhere in this photography business. I have a few little sessions lined up (at least 3) and it feels good. I've done 2 very recently as well. I want to get enough portraits so that I can start putting together a portfolio! Any advice on how to do it?! I mostly do nature, but if I'm going to be showing it off at studio's, should I strictly stick to portraits?!...or leave in some of my other work for them to get an idea of what I'm about? Any imput would be appreciated!