Fiery Dance - Level Up Move
Solarbeam - TM Move
Sunny Day - TM Move
Morning Sun - Egg Move
For Morning Sun, raise a Beautifly to Level 20 so it learns the move and breed with a female Larvesta.
That's it! You only need to breed Morning Sun, as you can learn the other 3 moves quite easily.
I'm not that great at competitive, but here is Smogon's main moveset:
Volcarona @ Leftovers/Lum Berry
Nature: Bold (+Def, -Atk)
Fiery Dance/Fire Blast