Your efforts should match what you hope to accomplish. If you want to be a writer. Finish your book first. If you are working on your website while writing your book, make sure that you devote more time to writing your book than building your website. The same goes for your marketing.
If you want to build a website first to sell the product, that is fine if you sell other people’s products. For example, there is. A new gas station is opening down the street. Before selling gas, lottery tickets, coffee, and Cheetos, they need to build the station. I agree it would be odd to drive by and see them selling Cheetos, lottery tickets, and coffee outside of a half-built structure with construction going on. It would not be safe for the customer and visually displeasing.
Your art is different. We are authors, and authors create books first, websites, and covers after writing. This is a hard teaching because many website developers want to tell you otherwise. Well, the good news is this. I have sold more books without a website than I have with one. Well, the reason is this, I don’t have an author website. I have homes for my digital products. I have places that you can find me online- Check them out here. I plan on building a new website and hope to have it up soon, but first, I have to finish my next book.