I thought you might have been talking about the ghosts in the cells, but then you said you were on level 2. I was on level 3 shortly after killing Fergus. You may have missed a few things if you really are on level 2, so starting over that close to the beginning is not a big deal. If you talk to the skull first and get the quest to kill Fergus, he will reward you with a cap that boosts your luck (and some experience points).
Did you find the (single use) healing and mana shrines off of Fergus' room? Are you hitting the alt key after clearing an area, to make sure you have not missed any hidden potions or loot? There are a few hard to spot potions around.
Anyway, if you have trouble the next time around, just ignore the ghosts for a bit (the minimap will show if the cells' inhabitants are hostile or not). By that point you should be close to going up a level, and just continuing through the corridor and dealing with the prisoners and guards (and optionally the spiders) could get you there, which should help a fair bit if you then went back for the ghosts.
You could just skip them, jump down the pit and come back for them later, but by that time they would not give many experience points (the higher your level is compared to an opponent, the less experience you get).
For the beginning of the game, I would focus on melee skills and abilities. You will level fairly quickly at first, so can start concentrating more on intelligence after you have your other stats up enough (the
Beyond Divinity Strategy Guide contains a description of the effects of the primary stats, and recommendations for stat point distribution). The more powerful spells start becoming available in act 2, which would help mages not be so short on mana (you could also have your mage use a bow for a backup, to help keep them out of harm's way).
