I've been doing a ton of "internet research" the last few days as I've pieced together a quadcopter and I see the recommendation for the Hubsan X4 all over the place.
Here it is on amazon for $35. I'd also get
the crash pack which has spare parts for when it breaks which will happen and another battery. He'll probably break props the most so if you could source some more of those independent of the whole crash pack that would be ideal. I bought
this little guy last week and am still waiting for the spare parts to arrive. I just broke 3 of the 4 props and have just one spare left.
I'm building a 250mm size quad but haven't flown before and am considering buying the Hubsan to play around with and hopefully learn until all my parts get in. There are a few different models to be aware of, the H107L is the basic one, H107C has an onboard camera that will record video, and the H107G has an onboard camera that you can use for first person viewing (FPV) to fly. If I bought one it would be just the most basic one since price is lower, then I'd buy more spare parts and batteries.
Here is a bit more info on the Hubsan, a bit of a starters guide.
I'd be sure to try and source it from a US based retailer since it may or may not arrive in time if you get it from China.