You can get significant abilities to copy from the Fallout Bobblehead cards, or you can simply use fan-favorite EDH cards like Mind Stone and Solemn Simulacrum
The main issue is that after using Flare Blitz once, it needs to add Fire Energy again
While not every combo is the most realistic, and some take a fair amount of setup to get going, there are a few that are a bit better than others
For regular upgrades I highly recommend: Vito, Thorn of the Dusk Rose, Mondrak, Glory Dominus, Anointed Procession, Parallel Lives, Eerie Ultimatum, and you can also run the Cat Oven combo with Cauldron Familiar + Witch's Oven + Clock of Omens, and there's the Ballista Combo Heliod, Sun-Crowned + Walking Ballista, and finally the Exquisite Blood Combo since the deck already runs the other piece Sanguine Bond One Down, Three to Go
Sokka will count himself as an Ally for his second ability
Seven mana for a 4/4 flier usually means youre getting some kind of useful ability or keyword on top of the vanilla creature