I built a new PC and I went with the cheapest ram possible ($50, 4GB) just to get it running while I shop around for ram. Is 2133 really that bad for gaming? I'm thinking of just getting three more sticks of 2133.
I wouldn't say it's bad, we are just seeing major diminishing returns on "faster memory", especially when we consider the escalating prices. Unless of course you like seeing high benchmark numbers, with little real world improvement. Basically I wouldn't worry about it.
haven't had a chance to play with DDR4 yet (it's in the mail) so i can't speak with experience.
However I can say that memory speed does play a decent part in newer games. I just completed a series of benchmark test with 8GB, 2x8GB and 4x8GB of the same DDR3 1600 ripjaw.
No games made and difference at all with capacity (nor did it change single to dual channel) but when i tried the same test with 2x4GB of Corsair Vengeance LP 1600 i got about 3-5% increase in fps. The difference is being simply the timings.
Better ram will increase performance, but you aren't going to be hurting with DDR4 2133 - it's just not as fast as it potentially could be.
Where you would see a difference for sure is in rendering. Not only will that take advantage of more ram, it will take advantage of faster ram, and multichannel memory.