Should I link my website to others of my websites?
Getting links pointing to your website is essential if you wish to achieve your goals. As you have probably already found out, this activity is not simple.
That is why if you already have a websites network, it might be very useful to rely on it. This will save you valuable time.
Think about optimizing your linking strategy between your own websites. Linking systematically all your websites at the bottom of the page is not necessarily the best strategy.
For example, you can publish articles with original content (no duplicate content) on your websites B, C and D in order to focus on a site A and popularize it.
In a very competitive environment, it is in your best interest to have a pretty qualitative topical network in order to benefit from a reliable lever of development.
One of the major interests is to fully master the content, environment and links text anchors optimization. Not to mention the guarantee in the durability of the netlinking media.
If you have a group of websites, go for it!
If you don't, then create it and maybe someday you will get not only one but many results in first position of the search engines.