It seems like a mistake or an oversight that there's no way to grind even small amounts of stars/milk from like arena battles or adventures. Other games from this company, for world events, there was always a way for F2P people to at least be involved. Yeah, you're not going to compete with the $$$ folks and win the top prizes, but you could always compete for the mid- and lower-tier prizes with some dedicated grinding.
Like maybe if arena chests dropped 10-20 milk/stars, and you could get a 1-5 milk/stars per adventure battle. SOMETHING.
What's weird is this kind of makes me not want to spend $$$ on the game. Because I'm calculating how much money I'd have to spend to get enough gems to accelerate all the milestones, and the prices (in gems) on everything is so high. It doesn't seem worth it.
I understand they need to make money, but it's like no one at the company did cost/benefit analysis, just slapped some numbers and called it a day.