Actually, as Calinda suggested, you don't really need big tanks... All you need is a full stack of paladins and the phantom spell. Each phantom image can resurrect the orginal stack, so you will hardly ever come to some problems.
Paladins can be found very early in the game. The island should be called Scarlet wind. There is a Camp, guarded by a tough army, which is easy to kite away from it.
To get back on topic myself, I second the opinion that trading isn't that important. Money is plentiful in this game
