More and more games are CPU demanding, a i3 with a r9 380 is not a great combi, take for example CSGO, if u run it with dual core and some 250$ GPU it won't get u the best performance, as the CPU will bottleneck the gpu quite abit.
Also why a 750 Ti 4gb, get a 950 OC 2g, as that gpu performs better, same price range, and 2gb is more than enough for most games.
That card combined with an i5 and you're good