If you start with Meltan, evolve it into Melmetal as soon as possible
If the gift creates a permanent (like a 1/1 Fish token), it does so upon spell resolution, which comes after the point at which you've already chosen targets for that spell
Of a demonic entity upon you, burdening you, and keeping you down
Doubling your mana at such a lower cost lets this deck seize an early lead and drown the table beneath massive monsters before they have a chance to react
Of course, Dockside Extortionist, Smothering Tithe, The Reaver Cleaver and Cavern-Hoard Dragon are among the better options for a big, bursty turn, but its the continual generation of treasures that helps the most