Hello @brojustaverage and thank you for your question...this is really hard.

Summoner Lorna. Not expensive and can help you a lot in low to mid mana games (plus I love life)

Common: Pelacor Conjurer. This card is ridiculous, I cannot still understand why it's so cheap. At lvl 10 4 skills + antimage is a nobraino.
Pelacor Deceiver: most underrated card of the game. A beast at max level, probably one of those card you won't appreciate until you peak diamond.

Rare: Meerdali Guardian, overall one of the best support I have seen around. It's complete and for its mana it feels like investing in bitcoin in 2017
Diemonshark: he is the husband of Meerdali they walk together just to make sure to win every mid mana game

Epic: mmmmm this is hard but I think.... Dax paragon because I love Pelacor Conjurer & then Onyx Sentinel. Onyx is a beast in low speed games I just love him.

Legendary: Almo Cambio. This guy is so funny..if there is a game with Enrage it just tilts your enemy. Whatever they pick they are screwed (most of the time you go for mage vs Enrage)
Just to show some love to CL: Uriel, this card is just amazing. Go with Chanseus and Shieldbreaker in last position and he will solo kill whole enemy team