I am going to recommend that you start with a color print film that uses C-41 process so that you can have it developed at a local or mail order lab for the lowest cost. Just for your first couple of rolls. I would also recommend going to Youtube and watching a 120 film loading tutorial or two. It couldnt hurt.
The first thing to learn about 120 film (especially compared to 35mm cartridges) is that IT WILL UNROLL ITSELF UNLESS YOU HOLD IT PROPERLY when loading. Once you've dropped the spool and you've got one end of the paper in your hand, it's kinda dead.
An awful lot of electrons were terribly inconvenienced in the making of this post.