There are many ways to produce Kindle .mobi files. One method is to create a MS Word file and to convert it to a .mobi file (using Calibre or Amazon's own suggestions).
It is not easy to produce a kindle file from MS Word. If you start with Google Docs, you're going to have to export it to MS Word (don't export to PDF).
Calibre is pretty powerful; it can convert your MS Word file fairly well. If you don't have MS Word, you can export from Google Docs to Open Office (Libre Office) file format .odt. Choose File --> Download as --> ODT But my experience is that ODT to .mobi doesn't work that easily.
But expect to spend some time testing and previewing your Kindle file. It will take a good while to learn how to get it into mobi format (or epub format). Alternately you can pay someone $200-$300 to handle a simple ebook conversion.
If you are comfortable with some html, you might try pasting the ebook contents into Sigil Editor. https://github.com/Sigil-Ebook/Sigil/releases
Tip: It can be easier to make an epub file first and then convert it from epub-to-mobi. (Adobe Indesign can produce an epub file, as can some other programs).
To convert from epub to mobi, you can use Amazon's own Kindle previewer tool https://www.amazon.com/gp/feature.html/?docId=1003018611