Popular zones as a tank

[Seeatee]

First off let me apologize for making so many posts lately I just returned for the first time in many years so I am left with a lot of questions

What level as a tank can you go Into the popular zones and find a group tanking. I currently have a 20 warrior and a 40 sk and they are both kind of at awkward in between levels, the war about to head to mm and the sk to com, if I go to mm at 20 or commercial at 40 would I actually find groups there? Should I hang back in the previous zones a few more levels? Basically as a grouping tank what is the zone progression and when do I head there?