Well sulfates in general are harsh and drying, so you want to try and stay away from them.
And as far as shampoo suggestions, if there's a Whole Foods near you, I highly suggest the "Whole Foods 365" organic shampoo! For whatever reason, it's about $2.50 a bottle (same as sulfate-filled shampoo) and it works great! This is the least expensive option I've found so far. If you want to venture into more expensive products, you can try Mop c-curl, Deva, etc.
Oh oh! And if Whole Foods is too far away or something, Target has an organic line called Giovanni that's aweeesome as well
it's a little more expensive, like $8, but it's awesome too!