I'd like to start of by saying, that this post is not about having more cards, skins, tournaments, adjusting bugs etc... yes there are very important but I will talk here about those side things that you don't really notice but are pretty useful.
Most of the CCG's do not have a "Global Chat" and can understand it to some point, but I do think that every game should have one.
If you would implement a global chat and made at the moment make it into a "Global chat" and "Support/help" where players can ask the veterans for some tips on cards, decks, etc... Yes the reward system for ranked should be implemented as well, the thumbnails for the decks aren't really a big deal, because you can easily overlook it.
For me personally having to chat with other people while playing games is the best thing, as I said most CCG's do not have this and you must add a friend after a game, and while in the game you can only use the emotes. As well to the global chat, if possible I think you should put a chat in a match as well, it gives you a bit more freedom so to say, or at least I feel like that. Being able to compliment an opponent for a good play or tell him that was a bad move, and help him if he is new is pretty useful in my opinion. Not sure how the rest feels, but there must be someone who agrees with this.
Daily puzzle solving quest which will reward you like 10 pieces of gold or 5 for completing that daily puzzle.
Lore, I am not really sure if there is any lore, but yeah, lore is always nice to have, it feels like you're in the story, it makes you more interested in the game.
Improving the text for effects of a card, and adding the ability to zoom in on a card and hover over an ability and then tells you what it do, it's handy if a card has more abilities, or just post both effects of the cards on the side, and if it can summon a new card, you should be able to click on it and it will show you that card, that will be played if you play the card you wanted to.
In game tips, of some sort for new players, even though the game is not hard to figure out.
These were just a couple of suggestions that I thought of in like 20 minutes, I haven't been playing for long just for like 2 hours and I have yet to explore the game. On the side note if anyone would like to be friends, feel free to send me a request, same IGN.
Thanks for reading, NationalArmy