I used to have a Bernette 65 and she and I had quite a few go arounds! I would get the tension just right then after a few minutes of sewing I would have to fight with it to get the tension right.
Get a machine with auto tension and a needle threader. Also, a few decorative stitches will come in handy. Check Greg's list. I have a Bernina serger which is awesome so I do like the Bernina line. I have a Babylock and love it.
If you can buy from a local dealer they should offer support and classes. But, if you belong to a guild, maybe someone with the same type machine would be willing to help you.