This is an odd question for me as I skipped most of the kind of "in between" stages. I never bothered with cig-a-likes so Ego batteries weren't a milestone, they were my first steps. I got mine in an Evod kit, so BCC's weren't big for me either, I started out with them. I've still only had juice from my local B&M, so that's out.
I guess it was getting my eVic that first made it "easy". Interestingly, carto tanks were an improvement of sorts for me, which seems to be a step back for most. The lack of dry hits is the reason for that. I chain vape so I dry out Evod/Protank atty's really fast and get many a nasty hit. The carto goes for a good minute before I have to prime it.
More recently, I got my first RBA, the RSST, and oh my evil, black metal Jesus does it make a difference! I've had an RDA for a while, but it isn't viable for all day as I have to leave the house some time. I can't chain vape it, which is probably a good thing, but the flavor is just awesome. I'm totally grabbing an AC9 in the next few months because of my good experience with the clone.