There are many great ways to earn money online all which need much learning and keeping up to date with what's new. Many Webmasters take advantage of what's popular in the news. Both ends of the stick, being the on the positive end, which may include weight loss, looking beautiful, stock market going up, training pets or child behavior, etc, just things where the outlook is positive.
The negative end which some take advantage of are disease outbreaks, war, world end, religions, celebrity deaths, etc to make money. Doing most of the things that may or may not be controversial to the public, or morally questionable would fall under this category.
There are various niches that work most of the time which have consistent income, however, you have to at least pick only a few and have your focus directly on them for a period of time before you pick a couple more. You don't want to overload yourself to the point where you can't keep up with what's expected of you, as far as subscribers, client's and search engines goes.
Do your research. Learn the niches you wish to specialize in, know your competition and what some of their sites look like, create lots of your own unique content relevant to all of your niches and subscribers, and always be open to constructive criticism.
BUT the TRUTH of the matter is, and the understandable reality is... When asking a direct question about best niches to Webmasters, you aren't going to get a direct answer, because by giving up the very information that is making them money, will ultimately impact the saturation factor, therefore would result in a decrease in sales for them.
It's awesome that you're here, proving you're willingness to learn! Just make sure you do your very thorough research, and learn everything you possibly can on the niches you choose.
Best regards,
NaturalWriter