which mobo and which graphic card to for with i3 2100
This depends on your budget more than anything. I don't think there's many GPU's that will last 5-6 years. Maybe if you sink $550 into a 7970 you might land somewhere close, but I doubt it.
Motherboard - Z68 would be my recommendation, purely so you can upgrade to an IvyBridge processor if you ever wanted to. Z68 offers the most features of a Socket 1155 motherboard.
Posting your budget, and place/country of purchase is probably going to get you the best build advice here....