you've wasted too much time, man. In general, a good niche is a niche that you can rank in, fast and without headaches, with the resources (time, money, and patience) you have available at your disposal. Oh, and it also needs to be a niche in which people spend money, otherwise you'll have a hard time monetizing it.
Here is a good guide on how to find good niches:
https://www.blackhatworld.com/seo/niche-hunting-the-definitive-guide-3-600-words.1390428/
And here's a PDF file that I downloaded from someone on this forum an year or so ago, in which you can find over 1900 blogging ideas (niches) that are profitable...
https://ufile.io/ercx75wb
Just choose one niche that piques your interest, throw it into Ahrefs (or any keyword tool that you like) to find a few good keywords to structure your site around, create and publish some content around those keywords, have the content indexed, build some links to it when it gets indexed and stabilizes in the rankings, and you're done!
In general, you will want to focus on niches in these HUGE markets, as this is where people spend most of their money in, and these markets also get traffic around the clock so you'll never run out of traffic or keywords to write content on:
- finance
- health & fitness
- education
- pets
- business
- medical
- relationships
- technology
- travel
- self help / self improvement
Although... be careful with the medical / business / travel / finance niches as they are very competitive, so you'll have to really nail your keyword research to find a niche in these industries that is untapped yet