if you get a 64 bit it's enough for a 3D effect i.e. Sega Saturn. Sega Saturn has a few good games.
I do recommend getting a Sega Mega Drive- even though it's a 32 bit 2D, it has some of the best games e.g. Sonic and Knuckles Collection.
Anything prior to Sega Mega Drive I would strongly not recommend since the graphics and game play would be too terrible to considered worthwhile
Since all the games and consoles would be all used, I can't say what the prices they would be (it's all ebay from here). I do recommend not to spend more than £20 per game (£15 would be sretching it) and nothing more than £40 for the console (you can get xbox with 3 games for that sort of money)
Good luck