Never used one myself, but I guess you are looking for something like this
http://www.ebay.co.uk/itm/FTBO-G10-3-axis-Carbon-Fiber-Handheld-Camera-Gimbal-for-Canon-5D-Ready-to-Use-/191621752916?hash=item2c9d8be854:g:RsIAAOSwNSxVbmSX
I'd visit my local camera shop and seek their advice. Get them to demo a few within your budget with models that suit the 70d, although most seem to be geared towards the go-pro.
Sometimes the stock can be limited, and the pro ones are a hell of a price.
3 axis are probably the best and ebay the cheapest.
Lets know how you get on.