lose or profit is depends on the players getting win or lose
of course invest in gambling site is so risky
if whales come and they win big you will get lose with your investement your money will decreased
While this is somewhat true, I wouldn't say that it is "so risky". While whales might be able to take all your money, eventually you will gain it all back due to the house edge. The main worry is not whales, but exploits in the site that let people take money without any consequence.
As long as you choose a secure, well trusted site it should be fine.
How much money do you want to invest?