I would say buy a few samples of different kinds types and weights, make practice sandwiches and quilt them. Different threads give different types of looks so you might just like some over another. polyesters tend to be shinier than cottons. Every person has their own tastes. You might like isacord, you might like superior, sulky, king tut, star. There are so many to choose from. I have only practiced with sulky variagated 12wt and 30wt cotton and guttermans cotton, but i have heard great things about isacord but haven't gotten around to buying some, my recommendation is to try different things.