FreeRealms is a good game. It's worth checking out if you don't mind cartoony games, especially if you have young kids. But its method of generating revenue will ruffle some feathers.
It's not a bad method, but it has a significant problem. Non-paying players are likely to be annoyed by the pay-to-play content staring them in the face all the time.
Losing a non-paying player matters because that players can tell people he or she knows about the game, and those people might end up being paying customers. Non-subscribers are a significant part of your marketing.
Another reason is that some players might not enjoy the game enough to pay early on, but become willing to pay after they have invested more time in their characters or experienced more content. For example, I didn't come across FreeRealms' tower defense games until after having played and explored a good bit. I enjoyed those mini-games a lot, and my hands-on experience with the full variety of mini-games in FreeRealms would factor heavily in my decision of whether or not to subscribe.
Obviously, you don't want the pay-to-play content to be "out of sight, out of mind" either. But there's more customers to be had than the ones you hook immediately. Smart placement of DLC and incentives in a "free" game includes focusing on the players who you won't catch right away or even at all. Try not to annoy players by advertising what they don't have access to every two minutes.