Yeah, get the booster packs early, cause the easy ones to get in the boosters are also obtainable from NPCs. This will save you the grind time to win them. Just FYI, you can only use 1 * cards and one 2/3/4/5* before you get 30 cards. When you get 30, you can use four 2 * cards and one 3/4/5 *. At 60 you can use four 3* and one 4/5 * Look for NPCs that are low entry fee. 10-15 to start. Then move on to 20-25 when you can use 2 star cards.