I guess it is official: Tech is my favourite element. I only had a little extra money on Sunday so I picked up my preordered Gearshift, grabbed Chopper and Jawbreaker, and when I got home I realized all of my new characters (outside of the starter packs) were Tech. All three characters are really cool, but it makes my exploration in the game more limited. At least in the 3DS version, you don't need a Trap Master of a certain element to open elemental gates, just any character of that element.
After Tech, I would have to say Fire and Earth on equal footing, then immediately followed by Water.
Upon entering all my characters into the 3DS, I discovered I currently own 143 different characters - ie. One of every character Including different series or editions of some (plus a second series 2 Sonic Boom that glows in the dark, but the 3DS doesn't differentiate between them). Of course, come payday on the 15th, I will go nuts and buy everything else I can find - I just hope nothing becomes unavailableby then. Unfortunately, my local Toys R Us recently closed down, so I will miss out on Legendary characters and packs (unless I am able to order them online wihout paying too much extra).