Duke,
Your EarthTainer looks great!! Congrats.
I am not that familiar with the Sta-Green Mix you bought. Just make sure there is no "dirt" contained in the Mix - - you want a soiless Mix as your base ingredient.
As you identified yourself as a first time grower, I would suggest for "Year One" you stick with hardy, robust plants, to get your feet wet. Stupice is one I would recommend, along with Cherokee Purple. Big Beef is another hardy and prolific variety to try.
Raybo
p.s. I really like your dolly addition, as this will make moving it around and doing the "Tainer-Tango" midway through the Season much easier.