I know it isn't an investment, but in the last few years some "high risk" investment funds have appeared, and in them you can either lose it all or earn a lot of money.
Isn't this basically the same as gambling? Wouldn't it be faster to just deposit the amount in a casino? At least you'd be able to spend your earnings much sooner

There are many gambling sites that offering investment from their bankroll, I think the words "high risk investment" is if you directly invest in the gambling site but if you only play then the words "high risk investment" is not right, just like other said gambling is only game that we have play with money involve.
Nope I think it is the other way around, if the site is legit and trustworthy. There is more risk in playing in a Casino than investing in it. Just check the odds and probability of winning. According to the percentage, House have higher chance of winning, meaning if you invested in a Casino, there is more chance that you will earn profit than playing in it.