Often, decks built around Haughty Djinn run protection such as Slip Out The Back and Shore Up, ensuring it stays on the battlefield while also fueling its power.
You get Coveted Prize as a spicy tutor, Spoils of Adventure as great card draw, and Practiced Tactics for cheap removal
Spatial Merging gets errata to read "Place both of them in the same slot on the planar map" instead of "Simultaneous planeswalk to both of them." My main guiding principle for these house rules was that phenomena are random, one-time events, so it was aesthetically unappealing to have them sitting in a spot, waiting to be triggered
One mana turns into two the first turn you bring it into play, and then you just get two colorless mana every turn thereafter
More monsters
Artifacts such as Contagion Clasp and its bigger sibling Contagion Engine let you invest mana into proliferate triggers, turning them into engines your opponents must answer