If you're watching the price of bitcoin at the moment then you should neither gamble or invest atm. Just keep hold of your coins & ride this train to $5000 per bitcoin 
if you are not a risk taker , then yeah better to not do both. but when you want to make your bitcoin keep growing in high risk way , go for gambling. feel not safe to do that? just put your money on altcoins or ICO . you could adjust it anyway based on your condition and needs. but everyone agree that investment always more promising compared to gambling.Putting your money in altcoins may be just as risky except for the fact you can get out when you think you're starting to lose
But then again, if you're betting in small increments of your total bankroll it gets more and more simmilar.