Should I also sell on Amazon?

I'm writing my first eBook about micro-entrepreneurship that's called Start With A Side-Project.

So far I'm only offering it on Gumroad, I actively promote it since I'm a first-time author so I don't expect to be recommended by Gumroad.

How does the discoverability on Amazon works? Will I have to put efforts promoting it there as well? I might as well just focus on promoting my Gumroad page instead of promoting two links.