Okay. So doing this revolves a lot on the luck of the draw. It's almost like building a starter deck. What I always do when I open the packs is sort them by type (water, fire, grass, trainers, etc.). Then I take the one with the most types and see if there is anything worthwhile in there. Keep doing this until you have 2 main attackers, sometimes 3, and then throw all of your trainers in. Then, take a bunch of support Pokemon of the colorless type or of the same type of the main attacker and throw them in. Any cards that let you search or draw stuff (Budew SF, Bueary MD, Baltoy GE) go in. Then fill the remaining spots with energy. It's a good idea to have a good amount of energy so you aren't stuck throwing crappy cards at your opponent's Pokemon with 4 energy. I usually have around 15 energy, give or take a couple. And there's a solid Prerelease deck. Of course, if one of your main attackers is a 1-1 Steelix line you've obviously drawn poorly and are not going to do so well.