Welcome to ECF Dan. The KGo is a fine PV. The carts that came with it should hold about .5 ml of liquid (10-15 drops). When you fill them, drip into the polyfill until it looks wet but not like a puddle. I highly recommend that you get some cartomizers. They hold more liquid and generally give a better experience than the cart/atomizer combo. Boge 2.0 ohm, Smoktech 1.7 ohm are both good choices. Dual coil cartos will work too, but I think the single coils are better on a 3.7V device. With cartomizers it is important that they not be allowed to dry and the first fill is extremely important. The are several videos on youtube that show how to fill cartos and I recommend you watch them.
The CE2's are a whole different ball game. They don't have any polyfill and they give better flavor because of it. The coil is at the top of the carto, so the vapor is warmer than other cartos. They are easy to fill with a syringe, can be cleaned several times and will last for a few weeks. On the down side, they sometimes have problem wicking resulting in dry hits. Most people that use them will mod them to improve wicking. The easiest way to mod them is to remove all the seals from the top (there are three of them) and only use the middle seal with the groove side down.
And when you get cartos make sure you get a drip tip as well. While not necessary, it will make the experience better and filling easier.
Good luck,,,
EDIT: If you like a warm vape use 2.4 Ohm CE2's. If you're getting anything from MyVaporStore use the cuopon code J12 for 10% off until Jan 31.