I use an E-Power which is very similar to a kGo and is 3.7V like the kGo, but uses non-proprietary batteries. I have also used a kGo, I just dont own one myself.
The Boge 2.0ohm cartos work really well, but personally I like the Smoktech 1.7ohm XL cartos more. The one thing I dont like about the Boges is that they only hold 1-1.2ml of juice. The Smoktech 1.7ohm XL cartos hold about twice as much juice as the Boges do. I would def try the Smoktech 1.7ohm XL cartos bc they are awesome and give a great vape on the kGo and E-Power. Their designed for 3.7V PVs, like the kGo/E-Power, and they produce a nice warm vape with a LOT of vapor. Since they hold alittle over 2ml of juice, they last a pretty long time before you need to refill.
Hoosier sells them for a good price, and so does Crystal Clear Vaping. Crystal Clear Vaping calls them the Ressurectors, but their the same cartos, "Ressurectors" is just a nickname. The Ressurectors are the only cartos I use on my E-Power bc I find them to be very consistant and give a great vape. If you fill them correctly and not let them get dry, they can last a long time. On avg one lasts me about 1-3 weeks depending on the juice Im using, but Ive had a few that have lasted even longer. My longest is almost 7 weeks on one carto.
I buy all of mine from CCV bc they have free shipping which is nice when you just want to buy cartos, and if you buy a 15-pack you get a free drip tip.
The Smoktech 1.7ohm XL cartos (Ressurectors) also work awesome in the Smoktech Dual Coil tank. CCV and Hoosier both sell the tanks and they are really cheap and work well. You can get one for about $10 and it comes with a pre-punched dual coil carto in it and a drip tip. Personally I think dual coils suck at lower voltages so I didnt use the carto that came with the tank. The Ressurectors are the same size as a dual coil carto so they fit perfectly in the dual coil tank and I think they work a LOT better than any dual coil does on a kGo or E-Power. I use the Ressurectors in the 3.5ml tank and they work awesome. The 3.5ml tank is perfect size for a kGp/E-Power sized PV. It lasts me all day without needing to refill, yet is still small enough that you can carry it in your pocket. CCV and Hoosier both sell pre-punched Ressurectors too for the SMoktech tanks and they have the metal base on them like the dual coil carto that comes with the tank.
As for juice, SweeneyTodd said, its really subjective. What I like you might hate, and vice versa.
I would check BlueMist Vaping though. They are an awesome vendor with great juices. They have a huge selection, over 250 juices and really good prices, $5 for 10ml, $10 for 30ml. They offer sample packs which I highly recommend you get and you can pick the juices you want for a sample pack. They also offer extra flavor shots for .50cents more, and if you find a juice you really like you can get a 180ml bottle for only $30, which is an awesome deal and considerably cheaper than what most other vendors charge
If you like caramel RY4s (that's what I'm into 
