i kept moonblast and geomancy as well but i also hace misty terrain and then thunderbolt. the moonblast will be effective against most types although not all then theres the thunder thats also super effective.
It depends on what your team can counter.
If ferrothorn and scizor are a threat keep hidden power fire and thunderbolt.
If not,keep hp ground and thunderbolt.
The move set that my Xerneas has that I find most effective is Thunderbolt (electric), Horn Leech (grass), Moonblast (fairy), and Giga Impact (normal). I would reccomend this if it is possible to teach your Xerneas those moves -3-