You can progress through the game at a brisk pace without spending a dime if you space out your interactions during the day. Wait for energy to recharge, and you’ll be able to get more done without spending a dime.
Choose your friends wisely. Make space for those who will support you rather than keeping freeloaders around!
Letting the game optimize your deck with the best cards you have available is always a good option if you’re not sure how to do so yourself. It’s a good idea to do this often to make sure you’re fighting fit!