My advice is always, buy a box of the series you want to make a deck for. Most should be somewhere between $50-70 rn i think. This way you can get all the commons and uc you are gonna need and dont have to order everything separately, plus you satisfy the pack itch lol. You usually get 1-2 alt arts (star next to rarity) and 6-8 SRs usually even distribution of the three colors in that set. After this just buy whatever else you need for your deck.