Personally, I disagree with ىtellarℵerneas☾ℒuna☽. A good support Pokémon should help save the precious Mega slot, not use it (imo), so I don't think using Mega Audino is your best option. For a good healer/supporter, I recommend Chansey/Blissey.
Chansey Set:
Chansey @ Eviolite
Nature: Bold (+Def, -Atk)
Ability: Natural Cure
EV's: 4 HP / 252 Def / 252 Spd
- Heal Pulse
- Soft-Boiled
- Heal Bell
- Seismic Toss
Heal Pulse is the most important move here for healing active teammates. If you want Chansey to last longer in the battlefield, Soft-Boiled is mandatory. Heal Bell is for status-curing and helps if you're getting killed by poison/burn. Got Taunt'ed? Don't panic, because Seismic Toss has got your back. Compared to Blissey, Chansey is more fixed to the Cleric job, but does a very good job at it.
Blissey Set:
Blissey @ Leftovers
Nature: still Bold (+Def, -Atk)
Ability: Natural Cure
EV's 4 HP / 252 Def / 252 Spd or 252 HP / 128 Def / 128 SpD
- Wish / Soft-Boiled
- Heal Pulse / Toxic
- Heal Bell / Protect
- Seismic Toss
Although Eviolite Chansey is a tad stronger defensively, Blissey is a bit more versatile and frees up the item slot for Leftovers. You can run with a set similar to Chansey, or take a more offensive approach with Toxic & Protect for Toxic-stalling. The second set of EV's is there if you want to try Wish --- with Blissey's gigantic HP, it can almost completely recover any injuired party members. Again, Seismic Toss for in case an annoying Taunt-user comes into play, or if you just want to speed up the Toxic-stalling process.
