I could use some help

[grizzlypatriot]

Hello. Im new to the whole competitive side of pokemon.  So far I have 3 pokemon on my team.  I have a mega blastoise(special attacker). It knows Aura sphere, dragon pulse, fake out, and water pulse.  I have an Armaldo(physical attacker). It knows Protect, Rock Slide, Sword Dance, and X-scissor.  I have a Rotom-heat(idk what it would fall under). It knows Overheat, Protect, Volt Switch and Confuse Ray.  I really need help with picking my final 3. I was thinking maybe Sableye or a Gardevoir but im really unsure and dont want to make a poor choice.  Any help/advice/tips you can give me would be much appreciated!

Thank you for taking time to read this and help! Have a b-e-a-utiful day  :D