I'd get two 8GB sticks (2 x 8Gb = 16GB). I personally like G.Skill. Manufacturer's website says you can get 2133 and 2400 Mhz sticks. However, your probable future mobo change/upgrade might require other RAM unless you plan on getting from same H110 chipset.
Mobo might not be able to boot at 2400Mhz. If the mobo can't run RAM at 2400 it should *theoretically* down clock them to 2133Mhz, no guarantee though when it comes to how systems handle different RAM.