They’re PB’s #1 favorite way to include pay-to-win.
Cosmetics, chips for exclusive heroes (sign-in for ranked rewards, or exclusive contest heroes for progress), and various other goodies.
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Rewards do differ each week, although there is always the contest hero.
Information on what kinds of contest there are, can be found here
Those aren’t a common reward, but they aren’t a big problem.
Stamina is a big problem. Aside from natural regeneration, you can get a decent amount of it from weekly quest, and it’s available in small amounts from various places.
Those are pretty much garbage.
Coliseum and arena rewards are the main way to get them.
First 2 require a lot of patiences, regen themselves.
Crates depends on what crates 
Diamonds you can get daily from Arena and Coliseum rewards, or via real money (do not recommend)