I think investing is more risky than gambling because most of investing websites are just scam, but in gambling you have better chances to make your bitcoin grow. How about you guys what do you think?
You are getting it wrong. Gambling sites can be a scam too, so let's not take that consideration into account.
Investing is better than gambling. If you look at the mathematics, gambling guarantees you to lose some percent of your initial money in the long run. This is called the house edge. Trying to gain profit from gambling is purely relying on luck. Investing, on the other hand, is taking that house edge into your advantage. You are guaranteed to gain that house edge profit in the long run.
The challenge now is to choose the right site to invest. Definitely, do not invest in HYIP program. Invest in something like gambling site bankroll, or some promising new altcoin.