Activity tracker tips needed!

OpheliasPath

I was thinking about buying an activity tracker, but I can't really figure out which one to get. I've been looking at the fitbit ultra, which is $90 on Amazon, and it looks like a lot of mfp users swear to that one too.
I figured I would just see if there are any other suggestions? I'm on a tight budget, so $100 is max and thats one thing that's good with the fitbit.