Oh, so many choices and not enough time in a day to vape them all!
Welcome charlie and all you new folks
Questions to ask about upgrading - what form factor? Box/Tube/Stick? Do you want an internal battery or are you o.k. with replaceable batteries? How much are you vaping (i.e. how long of battery life would suffice?) What kind of topper are you thinking to use? Clearo/Carto/Carto Tank/Dripper?
I have iTaste VV3s and MVPs as well as a Sigelei Zmax V3 and a Vamo V6. Also have a couple of Spinner 1300s from my early days. The only "right" answer is the device which works for *YOU* I've heard great reviews of the iStick. I have Nautilus tanks, Protank 2s, EVODs and kayfun clones. I like rebuilding coils and I can do for all but the Nautiluses. My "happy zone" right now is leaning on the Nautilus (full-sized and mini) and the PT2s on the MVPs and the tube mods.
Good luck - do some research and have fun!