Does the msi z87-g45 support DDR4?

No.

DDR3, up to 3000MHz(OC).

More than 1866MHz or 2133MHz with CAS9 is not really needed though. You can see pcpartpicker for kits. Install as dual-channel. i.e. 2x4GB or 2x8GB. I recommend 16GB total to anybody who games (mostly future proofing).