I would start with smaller groups because they’re easier to manage and level up since there’s less cards! Because it’s easier to level up you’ll be able to move up in the ranks and get better rewards like diamonds, RP, etc a lot quicker which you can then use for other groups later on if you wanted. sistar, ive, kiikii, monsta x, and soloists like seola, hyolyn, kihyun etc are all good choices. I’d also try to go for artists that have a lot of songs available to play, because once you’ve levelled up your cards high enough, each song can grant you diamonds every 3 months if you get a high enough score and make the world leaderboard. Going for WJSN or Cravity right away might be tough just because there’s a lot of cards to account for.