How do you get 25 gems from dragon city?

it's easy too get 25 gems

first finish one level combats and you won 6 gems, level up more and you receive 2 gems and won on tournament combats and you receive 2 gems, do it continually(3x)

And you receive 30 gems

I HOPE I CAN HELP YOU TO GET 30 GEMS MORE THAN 25 GEMS