Google considers backlinks as the bed-rock of search engine optimization. Without backlinks, your site won't be found on Google - even it's found, it will be around page 20 or deeper where no one goes.
So, when building new sites, make sure that your On-page seo e.g. keywords in headings, high quality content are all intact - then go out there and source for backlinks because that's how Google will even recognize that your site exists and then rank it up.
This is a piece of advice though.