Gems, the most important currency on this game :). Many players are using them like there are no tomorrow… Some players blaming that the gem is very hard to obtain, but that’s not true in my opinion. You can easily obtain gems on this game.
You can get gem constantly by doing things below every day, there is no end to this thing.
From Kung Fu Arena
At first you only get 15 gems every time you win the tournament, but later the gem rewards increased. It’s refreshed every 12 hours so make sure you enter whenever it’s ready
From Social Battle
I believe you can clear one league per day (3 battle every 5,5 hours). Remember that the biggest factor is to use strong element on the battle, you can still win even if you have 4-5 level difference (you need to compensate it by your battle level though).
From Friend’s island
Sometime you will get gem from tapping the gift box on the friend’s island (only 15 gift box per day). I believe you can only get 15-30 gems per day from this method.
Beat the challenger or invader
There’s a chance to get the gem from those field battle. From my experience the higher the invader star, the higher chance of the gem to drop. The invader only drop 2-5 gems, but sometimes they also drop the shadow dust, make sure you banish it every time you see one.
This is also very good source for gems, however you need some of the rarest pet on the game to be able to get the gem. The pets which have gem quests are Laser Chameleon, Aurora Peacock, Firefrost Unicorn, and Universe Dragon.
Note: The gems listed on the quest reward is the MAXIMUM gem possible obtained, so you may obtain less than that amount.
You almost likely to get gem from the lvl 11 and 16 promotion test.
Tips: You can create gem production by simply doing things below every day
 Have only 1 log training (max upgrade)
 The rest of your training facility should be Skyhigh gym with max upgrade
 Don’t sell your duplicated pet, feed them to teen level!!!
 Train them on log gym first, this should take them to level 6 after 1 training.
 at level 6 move them to Skyhigh gym until lvl 11. Promotion test, after finishing it (and obtain the gem),keep them and sacrifice them on the pond of souls.
Note: if you’re lazy to “refresh” your log gym every hour, you can build more log gym so you can train more “battle level 1 pets” at the same time , however try to have more sky high gym than log gym (my setup, 3 log gyms and the rest are Skyhigh gyms).
Make sure you login everyday to get the rewards.
They’re not renewable, finish once and they will disappear forever. However they’re still worth doing. I rarely take them as soon as I finish the objectives, I encourage you to do the same so you will find significant increase once you take them.
Visit this page, the reward seems small (1 or 2 gems), however you will gather a lot of gems before you realize. They’re really easy to do too.
Some pets give you more than 1 gem, so make sure you check this after you have hatched few new pets. Rarer pet usually give you more gems :).
Hall of Fame
You will unlock this building on the process of expanding your island (3rd expansion IIRC). You need to gather a series of pet to get the rewards. Make sure you claim the reward once you have unlocked the building.
It’s like badges, but you don’t need any special building to claim the rewards. Make sure you see it and finish it.
Don’t spend your gem carelessly even if you can get them easily from the game. Here are my suggestions for you
Those are all my tips, if you have more tips feel free to leave it on the comment. It will help all players.