Boge cartomizers are the most popular. I love them. On Riva, since it is >450mah battery you can use any of these:
standard resistance (2.8-3.1) - longer battery life
medium high 2.5 - warmer hit, a bit less battery life
low resistance 2.0 - hotter hit, even less battery life
For me, thinner juices like 20% VG or less (i.e 80pg/20vg) and especially if the juice is fairly clear seem to give me the longest good performance with Boges.
You need to fill totally (like 18+ drops - I hold a tissue on the threaded end hole as a drip juice into the stuffing), then I clean it up, blow out into the threaded end to clear the air channel, sop up any loose juice above the stuffing. Then first the first fill I lay it on different sides for 15-20 minutes to make sure every bit of stuffing is damp (so I don't singe the stuffing). hen I just keep it damp with juice. When the vape seems a bit light or a bit dry - I add juice. Needs juice less often than carts. A Boge will work decently for me for over a week (which for me is 2-3 weeks since I alternate two of them). They won't last forever like carts for they are nice.
Drip tip is nice too! use to drip juice on the atty. Or a plastic or delrin one can be used as a mouthpiece on a carto (easy to remove to add juice).
Always make sure the threaded end of your battery is dry and clean before putting on a charger.