Ah, I remember the days not too long ago. I’m a fellow Magmar player since day 1, and you will come to appreciate the faction staples. I’m not as familiar with starhorn, but the two generals play essentially the same so my suggestions should be sound.
-Flash Reincarnation: This card is great at lowering the mana requirements of your burst and letting you play big creatures for cheap. Also combos great with Sunsteel Defender, if you want a cheap way to climb.
-Natural Selection: A very powerful removal spell, especially if you are already controlling the board.
-Young Silithar: Essentially the best 2-drop the faction has access to, for good reason. Rebirth with serviceable stats gives it good staying power, especially versus decks that use early control.
-Elucidator: One of the most powerful burst cards in the game, especially when combined with Flash Reincarnation and Thumping Wave. Very dirty combo and can easily close out games.
-Thumping Wave: This card will essentially sit in your hand until you have lethal, because not only does it provide 5 damage out of hand, it can be used to eliminate big threats. Turns minions into a 3/3 battle pet at the end of the turn it’s used. One of the most powerful removal cards in the game because of its versatility.
-Plasma Storm: Another incredibly powerful removal tool. In a game dominated by aggro, it is one of your few defenses. It is obligatory that you use the “muah” emote if you wipe an opponent’s entire board.
-Decimus: This is for you, Starhorn. Essentially what the entire deck centers around. Flash Reincarnation lets you get it out faster, and it of course combos with Entropic Gaze and Volcanic Spikes.
-Makantor Warbeast: The true savior, praise be unto him, x3 no matter what your deck is.
Edit: There’s other good cards of course, like Rancour, and Kujata in some decks. Also you should try and get x3 copies of most cards when you start building your collection up.