There are many different ways (formats) to play M:tG that have different rules for how to construct your deck and what sets you can use cards from
III - You may cast any number of spells from your hand without paying their mana costs
There is a bit to track with the wide range of counters you might use, but some colored dice do nicely to differentiate the counters
Instant Color tag templates(None) Instant (CTRL to add secondary) Land Qty: 33 (34 w/ MDFC)Price: 126.43 Cabal Coffers , : Add for each Swamp you control
Still, easy to imagine a world where you want a maindeck answer to Lessons, Momo, and Reanimator that still has game against landfall and this will work
Some of these types of spells only let you choose one option, some you can choose a few options, and others let you choose as many options as youd like