Relibale Deck for SDD

This deck works far more often than not in Worldwide Edition, Stairway to the Destined Duel. It gives a couple different options including Destiny Board (which the AI of the game is terrible at stopping). There's plenty of easy to summon and high ATK monsters to beat down your opponent. Cyber Jar is a great way to change things up if things are not going your way and can be searched with either Sangan or Witch of the Black Forest. Jinzo may stop you from using Destiny Board for a bit but it can help lockdown your opponent if need be.

I have Black Illusion Ritual in the Side Deck if you really want to bother trying to summon Relinquished, but I find he's really just useful for fusion summoning Thousand-Eyes Restrict to really lock down your opponent.

Other monsters in the Side Deck are useful in case you're still trying to build up cards. Gemini Elf, Slate Warrior, and Wall of Illusion can be hard to get multiple of.

The most powerful monster in this deck is Barrel Dragon at 2600 ATK and its special effect. Trying to destroy powerful monsters like Kaiba's Blue-Eyes is better done with effects such as Barrel Dragon, Cyber Jar, Penguin Soldier, Wall of Illusion, Tribute to the Doomed, and Mirror Force. You can use their power against them with Dark Necrofear, Thousand-Eyes Restrict/Relinquished, Change of Heart, Monstrer Reborn, Call of the Haunted, and Magic Cylinder. For head-on brute strength just use Copycat, Mage Power, United We Stand, and Metalmorph.

Your most dangerous opponent is probably going to be Ishizu Ishtar, at least she's the one who always gives me the most trouble.

This deck is honestly quite customizeable, tinker with it to find what works for you.