First, pick a theme for your deck
Stormtide Leviathan 6.5 One of the best lockdown creatures on offer
Whenever that creature deals combat damage to a player, its controller may cast a copy of the encoded card without paying its mana cost.) Watermark: Dimir Illustrated by Vincent Proce Standard Not Legal Alchemy Not Legal Pioneer Legal Historic Not Legal Modern Legal Brawl Not Legal Legacy Legal Comp
Some other suggestions: Angel of Despair destroys a permanent for about $3, good with Panharmonicon as well
They offer a wide range of real Pokmon cards, including Korean, English, and Japanese editions, at competitive prices
If a card thematically fits your deck (for example my Timeless, who are golems (earth rocks) use Fissure and Earthquake), and it is a weak TCG card, why not make it ~kinda~ part of the archetype