Best skylake mobo

Solution
You can overclock the i5-6400. A lot of OC novices are having a hard time learning (or re-learning) how to base clock and take manual control of memory timings (they limit overclock when left in auto). You will also want at least two frequency tiers up from baseline RAM for headroom when adjusting that base clock If your DDR3 is high end (like 2133MT/s or higher) it will be fine, otherwise the minimum DDR4 I would get would be 2666MT/s. <looking at you red jaron>

I personally went with the i3-6100 and K4/D3 and just used my high end DDR3 that I already had. If I had to start from scratch I'd probably get this RAM since it has descent timings, cheap, and enough speed to not be the limiting factor when base clocking.

PCPartPicker part list / Price breakdown by merchant

CPU: Intel Core i3-6100 3.7GHz Dual-Core Processor ($112.99 @ SuperBiiz)
Motherboard: ASRock Fatal1ty Z170 Gaming K4 ATX LGA1151 Motherboard ($107.09 @ Newegg)
Memory: GeIL EVO POTENZA 8GB (2 x 4GB) DDR4-3000 Memory ($39.99 @ Newegg)
Total: $260.07
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2016-03-22 18:13 EDT-0400