10mb or 10Gb? I'm going to assume the larger, but it is a difficult answer to give because everyone uses the phone differently. I use email, Web and have a few widgets running for weather and that sort of thing. Occasionally I'll watch a few short videos or download a nook book or two, and I use a little over 2 Gig a month. My wife on the other hand streams netflix all the time and uses 10+ gig per month.
Since you are new to android and will likely be trying out different apps and stuff, I'd go with a larger plan then you think you will use to start. It will be cheaper than paying for overages, and after a month or two you can reduce the plan if you need to.
Just my thoughts, hope they help.
Oh and welcome to AC!