Absol is bad without Mega so don’t use that unless you can do a crit build with 100% crit chance, Yveltal is not available in the current version of the game.
I’d say just look up the competitive sets on Smogon and maybe change them a bit for in-game. That’s my suggestion.
I wouldn’t waste the mega stone for Sableye. Not that mega Sableye isn’t good, but just not needed as it is already powerful with a Prankster, Will-O-Wisp, Recover, and Knock Off set. Mega Gengar would seem like a better choice for using the mega stone on team.
I would also replace Absol with a Ghost/Fire or Dark/Fire type, Chandelure comes to mind first as it is stronger than Houndoom. Also you might find Geninja with Protean to be really useful in place of Jellicent, technically a Dark/Water but would function well as a scout and can change typing when needed.
Yveltal isn’t available unless you’re doing a randomized run. Malamar, Spiritomb, Delta Charizard, Hydreigon, Krookodile, and Tyranitar are some replacement options you can consider until Yveltal is released.