So, should I get 8 gb of ram or 16?
16 is the sweet spot these days. Especially if you plan on gaming. Any more than that is just a complete wait of money unless you use it for a RAM drive. You could throw in 64 GB of RAM and create a RAM drive for VMware. But I'm just throwing stuff out there. You don't need to do that if you have an SSD or m.2 drive.
A note on your build though. Make sure you go to the motherboard's website and look at the QVL (Qualified Vendor List) and make sure your RAM will work in the board. Better safe than sorry. That's what I do.
Here's how you do that. Copy the part number which will be a long number like; F4-3600C17D-16GTZR. Now paste that into Newegg.com or whatever website you are using. Newegg, I've noticed is pretty good and showing that RAM based on the part/model number. Not sure about PCpartpicker and the rest. You could use Newegg to look at what type of RAM it is, and then enter that type of RAM into PCpartpicker to find out who has the deal. Sometimes Amazon might be cheaper. But due note, unless you have Amazon crime, I mean, PRIME you'll get gouged by shipping costs.