Heh it's one of my oldest games, made in 2005, but I still think is fun if you like card rpg games. About your questions:
1- gather artifact for sure. Then once you're level 10 or so you can try the tournament and the quests. The quests are the hardest thing!
2- Wisdom impacts the mana pool, willpower protects from enemy abilities, though you don't fight against other druid unless you're in the tournament mode
3- the items damage a bit during fights, but a lot if you lose. In general there isn't a way to save permanently the items, you can only avoid them to breaking quickly
haha sorry about this, but that is a very "hardcore" game!
4- no spells are the one cast by the druid. The creatures (avatar) have a level too. In practice all your avatar starts at level 1, but if you collect several of the same avatar (like the Succubus for example) the creature level increases. If you collect 10 Succubus "stones", your avatar will be level 2. From now on, whenever you summon it in the game you'll summon a Succubus level 2.
Hope that helped!