Either of the two niches you mentioned could work.
As for the learning part, it’s not complicated, but it does take dedication. I would say that you should loosely follow about four steps:
1) Find and read quality content. Locate high-ranked blogs in your niche(s) and read as much as you can. Observe how the content is written, the formatting, pay attention to what the writers have focused on, etc. The more fine details you notice, the better you’ll be able to apply it.
2) Test yourself. Try and write similar articles, on similar (or same) topics. Don’t simply copy and replace words, but try to send a similar message in your own words. If you like what you see by the end, run it through Copyscape and (if it checks out) publish it.
3) Listen to feedback. Everyone’s a critic nowadays, but that doesn’t mean that there is no value in honest criticism. Learning that there’s something inadequate about your writing is never pleasant, but it is always a learning opportunity.
4) Experiment. Some may disagree with me on this, but there’s no real way to predict when and if something will blow up. Once you get good enough at reproducing existing content, you will want to create something you haven’t seen written up yet. Do it. The article may crash and burn, or it may become the most visited part of your website. Either way, you will come out of it a better writer.
