Here, I found a better list for a Ho-Oh and Darkrai combination.
Pokemon:
3x Ho-Oh EX
2x Mewtwo EX
2x Bouffalant DRX (You can remove one of these, for another terra if your area is heavy in Darkrai)
1x Darkrai EX
1x Terrakion NVI
1x Sigilyph DRX
Items/Supporters/Stadiums:
4x Prof Juniper
4x N
4x Random Receiver (You can cut this for a 2-2 line of Cheren/Bianca)
2x Skyla
4x Switch
4x Energy Switch
3x Tool Scrapper (You can cut 2 of these for other options)
2x Pokemon Catcher
2x Eviolite
1x Max Potion
Energy:
4x Double Colorless Energy
4x Fighting Energy
2x Psychic Energy
2x Darkness Energy
1x Fire Energy
1x Water Energy
1x Grass Energy
EDIT:
Leave it up to me to forget the Dark energies *facepalm*
DOUBLE EDIT:
How am I so person today, forgot more cards.