What's the earliest/ cheapest type of ipod/ iphone I can use free Facetime with?

Most of my phone bill goes towards texting and phone my girlfriend, so it would be much cheaper to just buy whatever I need to use Facetime or whatever it's called to do video calls over my Wi-Fi.

What's currently the cheapest model capable of this?

Added (1). But which model of ipod? The very first one?

Ipod

Ipod touch 4th generation, you will be sure to find one on ebay for around 80

The iPod touch 4th generation, released in September of 2010, is the first one with FaceTime capability. Off of Apple's clearance department, it costs $179 for a 32GB model refurbished.