When determining which effects stop working and which are not, you need to read the card text very carefully (preferably in the Oracle!) Banisher Priest phases out, then the exiled card will not return, because Banisher Priest does not leave the battlefield, and the effect does not end
If you change that cube by even a single card, youll be lowering the power level of the cube, meaning that there is only one set of interchangeable or mutually playable cards at that local peak
Meanwhile, Tainted Indulgence and Thirst for Discovery each draw at least two cards at instant speed, so all by themselves, they can trigger all of our payoffs during our turn or at instant speed during our opponent's turn
Generally approaching people at a store or convention hall with "Hey, do you have trades?", "Hey, can I take a look at your binder?", or if you're looking for a specific card "Hey, do you have [specific card] for trade?" should be enough to get started
Thats a great rate if you ask me