Both atomizers (atties) and cartomizers (cartos) with 510 threading will work with a kGo kit. Dripping is done on atties, and while it produces nice flavor and vapor, there is a pretty big learning curve, it can be messy, and it isn't always convenient (nor is it safe to do while driving)
Cartomizers on the other hand are easily filled using a syringe, and vary in size, so some will hold just under a mil, while others will hold up to 5ml or so! There is a learning curve with those as well - you'll over fill or underfill in the beginning, so it's best to have extras on hand.
Another option would be a stardust/vision clearomizer - those are super easy to use and fill - just unscrew the top and fill with your juice, screw the top back on & vape!
There are a ton of options - does your friend still vape? Either way, ask him some questions - he should be able to point you in the right direction as well as show you in person how to fill and use whatever you choose to use
YouTube is another great source of information - you'll find tons of videos to show you how to fill and use whatever you choose, and of course, this forum rocks
