These are the cards you should use:
Pidgey: This is your starter. It can find legend parts for you and is really fast.
Pokémon Communication: This is important to find the Pokémon you need, and can also search out legend parts.
Pokémon Collector: Gives you Pokémon to use with Communication, but also Pokémon you will need.
Jirachi/Shaymin: This is a combo that speeds up attachment of energies. Get energies in the discard with Junk Arm, Engineer's Adjustments or other cards, drop Jirachi and flip for energies and drop Shaymin to transfer them to Ho-oh. In theory you could power up Ho-oh Legend in one turn, but that is highly unlikely.
Pachirisu/Shaymin: Somewhat the same as the previous mentioned combo, just better. Bench Pachirisu with two lightning energy in your hand to attach them directly, and bench Shaymin to transfer them. A safer combination that is easier to pull off.
Ho-oh Legend is a horrible card though, if you want to win games you should avoid it.