Many suppliers will offer free samples of clay.. I get mine from Mid South Ceramic Company.. I use Phoenix clay and B-mix.. and both work really well. I don't know what other companies call it. Terra Cotta is indeed a difficult clay to work with.. I have only used it once.

As for consistency, I would say, if you pinch the clay and it kinda just breaks apart it's too dry.. and if you touch it and it sticks to your finger, it's too wet..

I think the best way to tell is to pinch it and if it moves with your finger without sticking to it and you can see your fingerprint in the clay, it's perfect for throwing.

I hope that helps.. heheh

I like it.. I think it might be too big on you though.. You should try making a transition line right where you're smallest on the waist. Make that area a little more form fitting and and it will look alot less "tenty"
I come from a loong line of big women.. and I've learned you shouldn't over exaggerate your clothing.. you can wear form fitting, it's different for every body type.. It would look good with a belt.. you just need a line to break it all up. Nice job though! The craftsmanship is very nice.