I bought a couple of mind machines and did a lot of research on the subject and my first suggestion is to try one out for a month or two to see if it works for you.
My second suggestion is to do your research. There a lot of mind machines on the market today and I'd hazard to guess that most of them are more toys than serious machines (cheaper isn't always better).
I tried a Mind Gear PR-2X for a while and ended up trading it in for a Comptronics DAVID Paradise XL. I found out that therapists/hypnotherapists/psychologists like the DAVID for many of it's features and I can see why, I'm very satisfied with mine.