I use Polystar, the thread bundle that came with my machine. And I have had success with it. Thread breaking is usually operator error for me.
https://www.amazon.com/Brother-Embro...=brother+pe770
Another bundle of thread I bought off Amazon was this pack. I use it with my Brother SQ9000 for the decorative stitches. The colors are beautiful and the thread is quite strong.
https://www.amazon.com/Embroidex-Pol...JWZV7TZ8TJRF2T