Hm... Well, you have both Gastly and Abra on your team, both of which are weak to Dark and Ghost. And Dark-types have the same coverage (Psychic and Ghost-types), so if I were to remove one from the team it'd probably be Gastly. But between Gengar and Alakazam, the former has more to utilize aside from just attacks, while the latter is slightly stronger and faster but doesn't have too much to really back it up with aside from Psychic-type attacks and Focus Blast (and Shadow Ball, should you feel like giving it your TM for that). So, one of those two probably.