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Hmm, I dunno. An electric type would definitely help a lot but it's a up to you. If you train your Pokemon well, you can beat the game with practically anything. Keep in mind that you adding another flying type to your team, which means 66% of your pokemon are weak to rock and ice and 50% is weak to electric.
I would suggest getting magnemite, seeing as how magnezone(if you have D/P/Pt) is absolutely awesome in stats.
It's also electric and has the most resistances of any pokemon AFAIK, and steel types are just awesome overall.
Is my favorite Pokemon!!! All my teams always have Alakazam as leader =P haha, BTW, going again to the question, you can add some power too, try out Tyranitar, Gengar, even if you want a electric, Ampharos would be fine =)