welcome to gamebanshee, sisu.
there's no connection between potions and gems, not as far as i know.
using two weapons is a frequently discussed issue here, just run a search if you want some in-depth analyses and opinions. ultimatly, though, it comes to your own preferences - roleplaying, powergaming or others.
here's a short list of duel-weilding pro's and con's here:
1 adds another attack, thus possibly lets you kill faster
2 lets you utilise more weapons, for on-hit bonuses (such as the use of dirty-fighting or cleave feats, or weapon-produced affects, such as disruption) or weapon-provided resistancies (such as lolth sting)
3 LOOKS TOO COOL! (#1 reason for me
)
1 decreases the chances to hit an apponent
2 does not utilise the high strength bonuses to the fullest
3 does not allow for shield AC bonuses
i'm sure every point on this list (as well as others) can be reachly debated over, so again, it's up to you
if you DO want to use duel-weilding, be sure to pick up two-weapon fighting and ambidextrity feats (or have a ranger as one of your classes), as the penalties for not doing so are pretty severe.