Build one website first. Try to rank it(hard in 2020).
You will face problems as there are topics already covered in your niche. If you have a new niche make sure people are searching for it. Competition is good as it shows that you can rank your website too.
Don’t believe in marketers who say they have earned thousands of dollars only blogging.
Blogging is not as easy as it was in 2006-2017. The secret to it is nothing. Think about it as a 9-5 job. You have to build backlinks and generate content. No rest for the first 8-9 months.
Since your website will be new, you would have to generate 10 times more content(need more people, maybe 3-4) than the other existing websites in your niche to rank it well and gain some domain score.
I am a blogger since 2014 and I am seeing a readership drop in almost all of my websites. People are generating more content, lengthy content, building thousands of backlinks to outrank my websites.
Build One Website First.
If you have success then build more websites and at a pace.
Generate Quality Content of every length (short to long)
Research your keywords
Build backlinks - tons of them
Update old content - every 8 months technologies/lifestyle/fashion change