This is right up my alley. Don't worry about it though, Shaymin has a horrible move range. It learns such few move types. Try one of these movesets, two for each form, in order from best to worst for each form.
Base Form:
Offensive Status
Seed Flare: High power, 40% chance to lower Sp. Def, STAB.
Grasswhistle: Puts the foe to Sleep.
Leech Seed: Damages the foe while healing Shaymin.
Psychic: Good power, high accuracy, chance to lower Sp. Def, deals with Poison and Fighting types.
Helper
Seed Flare: High power, 40% chance to lower Sp. Def, STAB.
Rest: Fully heals Shaymin, who ca then switch out and get rid of the Sleep with Natual Cure.
Sweet Kiss: Confuses the foe.
Aromatherapy: Removes Status conditions for your team.
Sky Form:
- Offensive Power
Seed Flare: High power, 80% chance to lower Sp. Def with Serene Grace, STAB, better accuracy than someother moves of equal or lesser damage, deals with Rock types.
Air Slash: Decent power, 60% chance to cause flinching with Serene Grace, decent accuracy,STAB, deals wit Grass types.
Earth Power: Good poer, high accuracy, 20% chance to lower Sp. Def with Serene Grace, deals with Fire, Steel, Rock, and Poison types.
Synthesis: Heals Shaymin.
2.
Seed Flare: High power, 80% chance to lower Sp. Def with Serene Grace, STAB, better accuracy than someother moves of equal or lesser damage, deals with Rock types.
Sweet Kiss: Confuses the foe.
Air Slash: Decent power, 60% chance to cause flinching with Serene Grace, decent accuracy,STAB, deals wit Grass types.
Synthesis: Heals Shaymin.