Google, Bing & Yahoo says that sites that have variety of backlinks get good ranks on SERP. This means you have have a combination of backlinks that are both nofollow and dofollow.
You should build backlinks from variety of sources like:
1. Forumns like quora & reddit.
2. Commenting on other blogs.
3. Article writing on Medium and Hubpages. There are many publications on medium that provides dofollow links. All you have to do is to search them.
Thanks & Regards,