Yes, 5m is probably a bit big for a beginner, good thing around 3m is you can keep it for your high wind kite as you progress!
I found 3m to be a good size, if you want some more power you can take it out in slightly higher winds, although I would recommend keeping below 15mph until you have the hang of putting the kite where you want it, and below 20 mph until you have more experience.
As for the Riot, I've already dropped the price and £115 is what I want for it. any less than that and I'd rather keep it as a toy for on holiday!
If you're on a budget you might want to have a look for an older beamer (2 and 3's should be below 100) and PKD Busters etc - all good kites and you'll get them for sub 100 I'd imagine. failing that, there's always Pansh!