Which Niche is easy to rank

The micro niche is a popular one, and you can rank a micro niche website easily on Google

I will not say go with micro niche.
As you mentioned you want to create a Guest posting website. So, first go with your own interest. if you know about digital marketing then do some keyword research on your competitor and try to find their low competition keywords that are getting traffic. Keep in mind every niche have competition now and it is up to you how you beat competition by selecting low competition keywords. Thats it. Best of luck from my side

Dear guys micro niches are good for startup in the online business world. Type in googlew keyword planner your phrases and see what it will spit out, something like 100-1k search volume or only 100 most of the times you will find there. But what's the real organic seo search volume what's your experience with them?

Then there is another obstacle , do you blogging with informational intent posts or commercial intent?
How do you make money on informational intent blog posts on cold traffic sales any experience?
Or do you getting more email leads with your informational content? For me build up an email list and then do email sequence then make an offer 1x time in a month is a too slow process today, then better rank good and make cold sales ias the faster way.

Making cold traffic sales th econversion rates will be better when you rank in Bing I guess, because of their elder audiences with a good wallet, they often use Bing.

Which methods do you use to outrank product based amazon category pages?

Is ‘self improvement or FIRE considered micro niche

Entertainment Niche is good for ranking.

Hmmm what exactly is an Entertainment niche? Movies review site ?
Or more trendic topics about every peoples life (something like that)- this could be a good niche for yt channel.
Entertainment or trendic topics blog posts are not commercial intent how to make cold traffic sales with them, showing 2 banners in the sidebar of your wordpress cms? .......

Or make it more like the media news sites are doing; under your blog post there you have a section like; Sponsors, recommendations etc,etc there you have 3-4 product reviews or a grid table of relevant produts, with that you need 20-30 different affiliate products ,so you can show different affiliate products to different trending topics blog posts.
Maybe that is allowed when you are approves as google news publisher or Bing news publisher...?

Can I do this as amazon affiliate to embedd a grid of topic relevant amazon products?
Here in germany some news sites have interesting tech products you never heard of, like these new mini houses from Elon Musk they costs 300.000€ but Musk sells it in US for $90.000 we are a poor socialistic country...

and many more of these tech gadgets. Where these news sites get these affiliate products?

you need to take start with micro nich

then you can convert your website in genral nich website