I also suggest if you plan on making a caster/healer mage, to use your damage charm in MAIN slot and heal charm in ACC slot.
If you are lucky enough to find a nice EE/INT damage charm, or EE/Heal Mastery damage charm, that would help boost your ACC heal charm, but those can be rare and a tad expensive.
If not, a simple EE damage charm in main and EE heal in acc will suffice just fine. Try to get +INT and/or +Heal Mastery gear, and stat INT as you climb. You may want to add your first 5 or 10 starting stats to VITALITY to give you a nice amount of HP later on, as hard-points to VIT will add HP each time you level up (but not +VIT from gear, that only adds defense)
If you have any more questions about the game or about character/item builds, feel free to shoot me a PM, I'd be happy to help!