there are really lots of ways. but take note that all needs effort and anything that has value. either skills, things, your mind, or time. the easiest i think are signature campaigns. there is also trading, but you need to be cautious with this one study the mechanics of trading first and make sure you know already a lot a bout it before you go and start trading big amounts. there are lots of articles about trading out there you just have to ask mr.google for it.
You are right, By hard working we can all get 0.1 btc per day, It's not impossible thing, but we should work and learn a lot of things by using internet to level up our skills and knowledge about cryptocurrencies and all profit domains. For exemple like trading, which it's a great domain to make profit. but you should learn first about markets and other coins and etc..
There is also gambling, but i don't consider it like a fixed source for profit, because it depend on luck.
You know what bud, i think gambling should not be part of or called as a source of profit, unless your such a lucky type of person that is. But if not, the i suggest that youshould not even rely on it for increasing your btc. Becausethe way i see it, in gambling you only lose more than what you gain. Not saying always though, but clearly most of the time. I know it coz I've been there. And also witnessed a lot of people going broke because of gambling and not just with bitcoins but with a whole lot more. But hey, this is just my own opinion and how i look at gambling itself. To listen to me or not, is the reader's choice. And besides, everyone has the right to do what they want with all the money they have worked hard for to earn. Goodluck to all in earning. Good day.
. Hope i helped even a little bit. 
