Pokemon 5th gen training & team advice help!!!?

Sorry I cant answer your whole question because i don't wifi battle or pay attention to tiers. For the dual types part it depends on there weaknesses. If u have a whiscash (water/ground) and sandslash(ground) they are both weak to grass. However if u had a Pidgeot(Normal/flying) and a snorlax(normal) it would be ok because pidgeot loses its fighting weakness. HOPE I HELPED=P