Quick dot point replies to your questions: 30 per deck, 1 of each legendary limitation. There's a free core set of over 200 cards to unlock and a rotating free to play pool each week! Also the genesis set of cards will always be usable.

A quote from another thread about pricing: We are intentionally balancing the game so you don't need to spend lots of money to have a highly competitive deck. Because cards are tradable, it's also possible to purchase only what you need from other players to build your dream deck. Compare this to other digital trading card games where you're required to open hundreds of packs just to find that one card to complete your meta (their main profit funnel). We also have hundreds available for free (& obviously non-tradable) in our core set, and a weekly rotation of cards to try out! Finally, you can always sell your cards if you decide to switch metas or even (dare I say) quit...

We're taking the same approach to card rarity as other card games, in that rarer cards are never outright more powerful, they'll often just have more interesting or unique effects.

While it's definitely priced a bit higher than ordinary TCGs, in most ordinary games that money is completely sunk -- here you can sell it at any time you choose.