How many sources of card advantage are good for your deck really differs on a case-by-case basis
2 Crux Of Fate Simple yet quite potent, if a Dragon deck has access to black mana, the inclusion of Crux of Fate is paramount
Madam Mim, Foxs Chasing the Rabbit ability allowed me to return a character from the board to my hand, which meant I could bring back damaged ones or trigger powerful effects from cards entering the battlefield over and over - when Merlin, Goat, which gains a lore each time it enters and leaves the battlefield, turns up you can see where the game really starts
Capable of summoning multiple 12/12 hydras by turn 5
Later in the game, you can spend mana to put the +1/+1 counters on creatures, which will, of course, be doubled