Thanks for the reply and your advice! I did just check out that compendium and it is really nice. I was going to start with a sample team but it seemed like everything was either HO or super bulky and I usually like playing with something in between (idk though maybe those are just the playstyles that excel in ubers). Plus I enjoy teambuilding in general.
This actually brings me to one more question though. I saw in the compendium that ferro isn't listed as a xerneas check. can you explain why? I'd assume after a geomancy gyro ball would do a shit ton.