The website age has nothing to do with this,
It really depends on your strategy and the website in question,
For a website with a few pages targeting high volume-specific keywords, I would rather have more links to these pages,
For a website with a mass number of posts/pages, I would focus on the homepage with some links to boost specific pages with higher volume/competition,
You can always start with the homepage to get an overall boost in authority & link juice, add some links to specific pages and make your strategy based on what you need and results you get