I'm with Cricket, so I get unlimited everything for $35 a month.
Small price, considering that I no longer use my laptop or tablet.
I like quick and convenient and my phone, is both.
I can turn my WiFi on and off at will, so if I'm someplace that has free WiFi, I'll turn off my phone WiFi so I can save on data usage.
I pay $35 no matter what, no roaming, overages or anything else, my phone just slows down if I'm close to my usage limit, per month.
Good luck!