One way to combat lifegain is with Sulfuric Vortex
A body for as long as you need, two lands almost guarenteed and a bonus card for two mana should that be the thing
Conversely, playing three or more colors is often correct in retail Limited decks, especially in Sealed, which very rarely have access to any fixing lands, much less the kind of manabase weve recommended here
Most notably, it means he's pretty much an automatic inclusion in an Ezio deck - and this is the other breakaway commander from the set, with more than 2,500 decks logged so far
(4/29/2022) Once an ability that causes a creature to connive begins to resolve, no player may take any other actions until it's done
Not sure what your pod/meta is like, but there are some enchantments and artifacts out there that can be a real pain in the neck against a deck like this