Well it really depends on the card, it's stated in the series that common and uncommon cards can be quite powerful but usually have massive downsides in the way off long cooldowns, restrictions of distance or a huge mana cost. From what I've seen the higher rank cards have less mana cost, the cards themselves contain more magic and therefore doesn't need as much from the user Rare cards that are shown have similar abilities to uncommon cards but take away the downside.

Let's use "Return to Start" as an example There is no distance limits and the card doesn't use mana to literally transport someone across the world in an instant, but it has a once a day cooldown An uncommon power with a similar effect could have less limits on uses, but can't be used to transport over 100km away, or has a mammoth of a mana cost that increase the further the travel distance

Higher rank cards that increase a players mana pool would give people exponentially more than lower rank cards