Things I feel you should invest in:
Alakazam, great attacker but low HP
Exeggutor, you have one but I use them a lot
Blissey, mainly for defensive but can attack quite well
Lugia, like Alakazam but more bulky
Machamp, poliwrath, Heracross,Gyarados,, Jolteon
I use any of these Pokémon most of the time though.