What ram to get for msi gaming 5 & i7 4790k

you can have a look here: https://ca.pcpartpicker.com/products/memory/

pcpartpicker has a good rating list with price. So it`s best for you to make a choice on that.

And from https://ca.msi.com/Motherboard/Z97-GAMING-5.html#hero-specification

DDR3 Memory DDR3 1066/1333/1600/1866*/2000*/2133*/2200*/2400*/2600*/2666*/2800*/3000*/3100*/3200*/3300*(*OC) HMz

You must choose a compatible memory: Make sure to choose a compatible one, same ddr type, and frequency(One of the number showed).

You should also fill the list of your computer parts on pcpartpicker list

It will show most of your possible problem such has: power supply has not enough watt and Ram dims not compatible with motherboard.

Happy to help you