The equipment with the highest mana value is Excalibur, Sword of Eden with a big if in its clause: It costs significantly less for each historic permanent you control, meaning that artifact or legendary-themed decks can cast it for relatively free
Sorcery speed is a bit of a drag, but if youre digging for something specific, Ponder is a great option
I actually had over 1000 energy cards at one point
This means phasing back in does not trigger enter-the-battlefield effects in the same way flickering or blinking would
I think Copy Artifact would be more useful, perhaps even Phyrexian Metalmorpth and those are just more examples of cards that are a little too situational, slow or hard to cast to be worth it
Notably, while both games have extensive microtransactions, these are free-to-play titles that have garnered huge fan bases precisely because they offer a free introduction to the game