What if you invest in yourself ? Or a business you know ? Bitcoin investments dont really exist because bitcoin is so volatile I guess.
You can count altcoins as investments too. Gambling is much better then HYIP though.
There are gambling sites with investment feature, you can invest as low as 10 mBTC. you won't profit much though if you invest low amount, the bigger amount you invest the bigger profit you'll make.
But we all know from past experience so many gambling sites disappeared after "farming trust with good features". It isnt recommend to invest for daily revenue on gambling sites, instead of you can try investing on future altcoins. Also you need to find affordable price on low rate, dont jump on train after prices skyrocketing. Gambling is for fun, enjoying from betting on your free time.That's why all known both investors and lucky gamblers agrree on this statement: Don't gamble if you can't afford to lose that money..
Both are profitable actually but you just have to be very careful not to expose all your investment to one kind only, investing in casinos are profitable since they have been operating for so long which means they were able to cope up with their expenses and continue to make money. You are the one to decide what to do because you can make a research in everything you plan, be sure you do your best to be successful as that is what we aim for.