It's unlikely that you'll be able to pick up every card available from the jump (at least, not without spending some serious cash), but here are the top cards that you should cross your fingers and hope for as you open packs
To make sure, close Omega AND Discord, then launch Discord first then launch Omega
The idea is, you play her and force an opposing creature to block one of your creatures, ideally, killing that creature and keeping yours alive
Key Cards & Sample Decklist : Pokmon (16) : 3 Ralts, 2 Kirlia, 2 Gardevoir ex, 2 Munkidori, 1 Drifloon, 1 Scream Tail, 1 Lillie's Clefairy ex, 1 Budew, 1 Mew ex, 1 Fezandipiti ex, 1 Manaphy Trainers (33) : 4 Iono, 2 Professor's Research, 2 Arven, 4 Night Stretcher, 3 Earthen Vessel, 3 Ultra Ball, 2 Nest Ball, 2 Rare Candy, 2 Bravery Charm, 2 Counter Catcher, 1 Super Rod, 2 Technical Machine: Evolution Energy (11) : 7 Psychic Energy, 4 Darkness Energy Matchup Analysis : Gardevoir ex is incredibly versatile