I'm having a bit of a quandary with this game.
I've put a total of $30 towards the game and that has allowed me to have my entire card collection at 10 (common) / 7 (rare) / 3 (epic) / 1 (legendary).
I believe that after you have your deck at 11/8/4/2 you just have to put money towards the game if you want to go higher. It just gets exponentially more expensive at that range to upgrade, not to mention Legendary card purchases.
So my question is, especially to players who've only dropped a few bucks and F2P players, do you expect to progress your deck higher, or do you play the game with the mindset that above-mentioned card levels is the highest you'll get?
I've only put in $20 to buy some gold for legendary cards. Apart from that I haven't put in anything and I've gotten two cards to lvl 12 (RG and barbarians).
Once you get to this lvl, you should focus on lvling your commons. It takes as much cards to get a common to 12 as it does to get a rare to lvl 8, so it's definitely doable free to play it just takes a bunch of requests. As long as you're donating as much as you can everyday, you should have the gold for the upgrade by the time you've requested enough (around 17.5 days in legendary arena).
It takes 400 cards to get a rare to lvl 9 and 800 cards to get a rare to lvl 10, so you can lvl those but it will take a while (1 month and 2 month of nonstop requests respectively).
Now that I've gotten those cards to lvl 12, my focus is on getting every card in my deck to tournament lvl and all my rares to lvl 8 so that I'm able to change up my deck when I want. It's not worth putting money into the game at this lvl as chests are weighted towards cards you have less of. So if I want my RG to get to 13, it's probably better to just request him for a month since I'd have to open a ton of super magicals to even get 1 RG.