Dominaria, Innistrad and M12 all provide solid cards that can fit in most decks, as long as you disregard the cards that depend too much on synergies (UR wizards,Burning Vengeance,Tribal cards from Lorwyn, etc.)
Dread Presence Dread Presence offers beneficial options whenever you play a swamp
The built-in Rebound gives you a guaranteed way to trigger the synergy, of course
Its Anguished Unmaking stapled to Lightning Helix
Citystalker Connoisseur was the perfect 4-drop for the deck, providing great defense, often hitting their best spell, and providing a Blood Token that could discard extraneous cards that were bad in the matchup
The likes of the "Spellslinger" Starter kit is no more than a couple of dollars/euros/pounds and often gets given away at events