I agree with Stabbey, pretty much. However, it does depend on the equipment you find/buy to an extent, as well as your playing style. If you are getting lots of vitality bonuses on armour, and rarely need a
restoration potion, then you don't really need to add more.
I held off using charms until I had great equipment, but by that time I didn't need the extra bonus. If you need a boost, and merchants don't have much in the way of upgrades, I wouldn't worry too much about using charms on poor equipment (though you will loose the value of the charm if you later sell it). Silver charms can be bought (I wouldn't use anything less than that) and gold becomes easy to come by as the game progresses. Gold charms can be bought, and found more readily, near the end of the game.
Between Magic Barrier and equipment bonuses, I never had a problem with resistances. For equipment bonuses I tended to prefer stat boosts to vitality/magic most of the game, but early in the game a few vitality/magic bonuses will be a great help. Playing a warrior I had lots of mana for occasional spells just from magic and intelligence bonuses on equipment.
differences between classes (minor spoilers)
Early Starter Tips (NON-Spoiler Version) (contains much of the information in the above topic)
