The Format known as Yugi-Kaiba is the earliest meta in the TCG, consisting of only Legend of Blue-Eyes and the two Yugi and Kaiba Starter Decks.
The Limited card pool means most decks are comprised of largely the same cards, with a lot of them being auto includes. There's no banlist, but there's a limited list, which are all auto-includes, except for the 5 Exodia pieces. There's also a semi-limited list, which is only Swords and Card Destruction, the former an auto-include at 2, and the latter is a staple also usually at two.
Historic decks aside, Control represents the overwhelming majority of the meta, particularly with Soul Exchange, and with a mill variant relying on Card Destruction, and some Burn variants.
This list was made by compiling the decklists at the YGO Format Library, going through the top event decks and seeing what cards where used and how often. Some cards did not make the list, but should still be considered, and to note that these are not the exact card ratios you'd use, particularly Side-Board/Main-Board wise.
This list is meant as a starting point, these cards are used in the OVERWHELMING MAJORITY of the decks, usually in these quantities. The mainboard trap cards are used in every single deck at full playset and so are most of the cards mainboarded.
Sometimes not used as a full playset are Soul Exchange, Summoned Skull, Neo, Battle Ox, and Wall of Illusion. Everything else mainboarded and/or used as a full playset is invariably in these ratios distributed between main and side board.
Most decks will at least consider running 1 De-Spell, rarely 2, never 3. The Wicked Worm Beast and Trap Master are common deck at varying ratios. Aqua Madoor and Ultimate Offering are also usually run.
Of note is that even Aggro and Turbo decks will use most of these cards, with just some minor changes to account for their particular strategies (notably, Dragon Turbo will swap in Blue-Eyes and dragon support cards), so anyone wanting to get into the format work their way from here with a rock-solid foundation.