I left game 3 years ago when meta was Cyber Angel and Gladiator Beast. Now I have this decks half builded and Aromage, no Synchros, no XYZ or Pendulum cards and a lot of expansion boxes.
My question is ¿ I have 10k gems, what should I buy?
Well, since you left long ago you missed some core synchro and xyz cards. Imo, if you want a cheap, easy to use tier deck go for Sign Of Harpies box. With 10k you can get all core harpie cards. Also, 90% you will just synchro Harpie Slash so you dont need all those extra deck cards. Use your sr dream ticket for malevolent sin (staple extra deck card). The rest harpie cards are f2p. Cheap kog deck.