Gambling is never an investment since its just a game with money involved unless if you decide you put your money to the house itself then its considered an investment and with that its somehow safe compared on playing gambling itself because you are on the house side which we all know who always wins therefore we could say that we could able generate profits when house is profiting too.
to me i think gambling can be consider as high risk investment. gambling is infact a type of investment but the most risky investment, because in gambling there is a very little role of your experience and your skill and you mostly depend on your luck in gambling. and no one can be lucky for every time.
What makes you lower the risk is by putting your money in gambling sites bankroll, investing is very profitable compared to making your journey of betting a professional gambler. Though the rate of return is not that attractive for people who can only afford a small amount of bankroll but it's constant. Anyway, we have our choice on what to do as long as we know the risk exposure of our venture.