Bear in mind that the Sorcerer class is undergoing a lot of changes in the upcoming 1.6 patch. What you do with your second bar depends a lot on the "feel of the character" that you want to have. Is your character a pure mage? Then you might want to add a second Destruction staff to go AoE, or a Restoration staff for some heals. Is he a spellsword, or a battlemage? Then you could add a greatsword and let him get close and personal with his foes.

There is a lot of debate and controversy regarding the changes to the class in the 1.6 patch, and the situation is still very fluid. However, it seems that stamina builds could be the most effective way to play the Sorcerer, so using a melee weapon might be the way to go. In which case I strongly recommend a two-handed one for highest DPS. On the other hand, pet builds also seem to be very favoured. In which case you will need to place your pet abilities (scamp/clannfear and twilight) on both bars, because they are toggles and otherwise they will be unsummoned when you switch bars. That means you will have fewer skill slots to fill than you otherwise might have expected, especially if by then you will also decide to add a Magelight from the Mages Guild skill line (also a toggle, so it will also take a slot on both bars).

Remember you can always change your skill depending on which enemies you are fighting, but in general I think AoE will help you kill mobs faster.