Put together, planeswalker support turns a few powerful cards into the backbone of a strategycommonly called superfriendswhere your entire deck is built around keeping planeswalkers on the battlefield and making the most out of their abilities
SARs, URs, and Gold Cards are usually 1 per several booster boxes
Since price is always a constraint, I think the better question should be, Whats a good storage solution within my budget ? There are fantastic solutions that will check all the boxes that you might be looking for but will also cause your bank to call you in concern
For a more data-driven perspective, we can consider the most-played cards in the Standard games of MTG Arena's Streamer Event
In case of Potence, Card not found kept it in check until it was restricted, and after that so called Turbo-Card not found decks rose into prominence, which could effectively lock out the Potence players pretty fast