I use the 901 flat tips from Johnson Creek on my Riva and it works great. The flat tips hold around 11-12 drops with blue foam and I top off often. Toping off keeps the flavor up there. The round tips that came with the Riva hold around 15-16 drops, however, I do not like the round tips. Re-filling your own carts is the least expensive option, but it takes a little maintenance. As for the the juice, order the better quality juices, USA made, and your atty's will work better - longer I am cleaning mine once a week and have had no issues. Look at the e-juice fourms and read the revews of the flavors since all taste buds vary.