It depends on the game TBH - but 9/10 the card is more important. I would probably go with a Core i3 6100 at the minimuml,and then upgrade as required although going with a Core i5 first does mean less hassle taking the rig apart.
There is also AMD Polaris which should be out in June or July which might be a better fit,as the cards should have much better performance/watt and you could use the IGP for the time-being.