Hi and welcome! Like others have said, at first I tried the cig2o and something called prosmoke because they looked similar to regular analog cigs. After wasting about $200 on extra batteries and chargers and refills for those 2 brands and discovering that the batts don't last very long for us heavy smokers, or they die all together after only recharging a few times, I went with an ego 650 mah because they last longer on one charge. I used ego-T tanks and cartridges but the flavor is muted on the regular ego 650 mah, so upgraded to the ego-Twist (which you dial up the voltage to get more flavor out of the tank/cartridge). The ego-T cartridges don't hold enough jucie to last me all day so I have several filled and switch back and forth with different flavors in them.
After a few months of research, I now also use Vision Stardust Clearomizers (many vendors sell their own/generic brand but most are about the same in performance). These hold 1.6 ml of juice and last longer (heavy
vaping like chain smoking LOL) than the ego-T type cartridges. I have several of these filled with different juices too, because mainly I like to switch flavors throughout the day. The cartridges and clearomizers can be cleaned and reused many many times. Lots of youtube videos on cleaning and dry-burn for the clearomizers and ego-tanks etc.
Good luck on finding what's right for you. It's a fun and interesting journey (costly too in my case LOL)