Build tank on the tank one, right click on the right click one, and magic amp on the magic one.

Pick a form and stick with it.

Well, these are how I would build the bleed form personally:

Bleed Form - Wicked Fury (most NB), Blood Curse sword, Asura Rapier, Shimmering Rose, Abyssal/Divine Soul, Otherworldly/Divine core.

This above one is if you wanna be lazy and just stand back and auto-attack without using spells. if you wanna go up close and personal, you can skip the soul and replace it with Asura Heart/Plate. Since you have Core, you can really spam your spells quite hard to rack up the bleed stacks, especially your ulti, and the int provided by core and rose strengthens your bleed (at least that's what I've seen from my own times playing with him).

if you don't want to focus so much on casting spells for dps, then you can skip core and soul, and get Asura Heart and Berserker Helm 4, which will boost your damage by a lot

After you've upgraded Bahamut Fang (and if you want to get Dimensional Core also), dump the rest into movement speed perk to make up for not having blink boots.

But that's just my opinion. Really, there are so many ways that you can play this guy, and usually with my build above I can tank just fine even in the bleed form

Thanks