Maybe I missed the response stating the obvious and likely most efficient way to earn Bitcoins:
Getting a job, earning fiat and buying bitcoins.
Maybe that sounds like sarcasm, it is not.
You can try all the other things suggested, but the amount of time that many of them take relative to the earning potential seem quite small, especially when compared to other jobs.
For example, trying to earn more Bitcoin from trading Bitcoin works, yes, but works better if you have more fiat to begin with. Also, just by earning fiat from a normal job, putting it in to crypto, and letting it sit is usually more profitable than trying to trade your way up.
Sure, we all hear the success stories: so and so turns $15 into $1 million trading Bitcoin etc.
Truth is, this is the exception, not the rule.
The knowledge and "luck", not to mention free time to stare at and study the charts, required to actually turn a small amount of money into a large amount of crypto, without adding money from an additional source, i.e., working, just does not add up in my opinion, and I say this from experience.
Even in countries where the wages are lower, New Delhi India for example, where I just read average income is $7,500 per year. Just think if you took a fraction of this, even $150 per month, or $1,800 total, and had been putting this in Bitcoin. I'm not going to do the math, but off hand it seems like you would have at least doubled or tripled or yearly income doing this.
I know everyone's situation is different, given skill set, home country and so on, and this may be easier said than done for some, so my apologies in advance for any insensitivities in this context.