I would suggest a 3-4 thread machine and make sure it has differential feed. I bought a used Brother several years ago for $75 with the above features. It works well and I was able to take a several-session class to learn to thread; about tensions; etc. Good class. I haven't really used it since but like having it. Not knowing if I would use it much (and that was what I thought would be the case), I didn't want to spend lots of $$. If you can find one with air threading, so much the better but I don't see too many of those listed for sale.