What Yugioh card(s) should I buy?

I'm looking to buy 1 or more cool but really powerful yugioh cards. I'm already looking into DaD for a cheaper price. I have all the cards from the dragon lord and marik structure deck, Obelisk (gb1URv), Horus lv8, Chaos Emp. Drag., Divine Neos, Darkness Neosphere, Exodia pieces, winged kuriboh lv 10, Dogma, and gold sarc. I know most of these cards are outdated (I haven't played in a while) but I cant get any synchro monsters cuz I don't have any tuners. I need something strong. I'm also interested in some sets of cards like yubel or any cheap booster box's around $50. I was thinking about getting the Kaiba duelist box.