The idea here is that you would keep gaining more mana, and if you couldn't pay it, you would keep taking more damage
When you buy these decks, all the cards will be added to your collection, so its a novel way to buy specific cards
For more deckbuilding tips, see: How to Build an MTG Deck and How to Build a Commander Deck in MTG and to choose the type of deck youd like to build, see Deck Types and Popular Deck Archetypes!
A starting build might look something like this: Creatures (22) 4 Crystalline Sliver 4 Muscle Sliver 2 Plated Sliver 4 Sinew Sliver 4 Predatory Sliver 4 Galerider Sliver Lands (22) Spells (16) Your big advantages over Merfolk are a better type of evasion Flying works against everybody, pretty much and Crystalline Sliver
Just as with that card, replacing itself with more sacrifice fodder is always great
20 SNAPCASTER MAGE Blue, more than any other color, relies on casting Instants and Sorceries