My choices, in order:
Chemical type:
Canna Terra
Botanicare Power Plant/Power Flower

Organic type:
Canna Bio, using the accompanying composted coco medium mmmmmmm *drooool
Botanicare Pure Blend Pro- you may want to also buy a bottle of Canna PK 13/14 to hit them with in flower, according to bottle instructions of course, as the PBP could use a smidge more K by many accounts.

These ferts are all very easy to use and will give solid results. IF you want to get fancy, run a complete cycle with the base ferts, keeping a log book, and then decide after harvest what to add next time- things like a carbohydrate supplement, a bloom booster, or a root stimulator are nice to have when you know your game and want to improve yield, but you need to know HOW to use them and how to read the plant forst.