You can save your gems for when a package arrives that you don't have yet, which can cost between 1500 and 2000 gems, or buy a wish item from the boutique, or exclusive items from the Wish Store, which you can find by clicking on the event. The Mystery Shop also has some cool items from time to time.
The heart store receives few updates, but over time you can get everything you like there.
Complete all the daily missions, or as many as you can, to earn coins. I like to buy the 9 red flowers every day and accumulate them, it's good for flower exchange events and also for sponsoring events. Sponsoring events increases your weekly gem earnings in the Lookbook Ranking Rewards.
These are my game strategies.
I hope I helped.