The yarn count should be around Nm6 – Nm8 (including Nm14/2, Nm15/2, Nm16/2, Nm28/4, etc.). These are ideal for a 7GG look and feel.
A much thicker yarn would be problematic due to needle breakage. Thinner yarn will, in general, work but will give you a looser fabric.
All yarn materials are fine to use on Kniterate if they have the right yarn count, from mohair to lycra. They should be wound on a cone and be double spun (single spun yarn will break easily).
We recommend knitting a test piece to make sure the yarn works. Every yarn needs different settings and some yarns are just better for hand knitting.
We can’t promise that every yarn will work for every pattern but, at least in principle, you should be able to use it with our knitting machine. We recommend yarns spun for industrial use.