You need to have both, dofollow and nofollow links. Nofollow links can provides trust to your domain.
SEO Point of view DoFollow- has special types of markup inside that tells the search engine like Google to follow the destination inside the link while NoFolloe-has special types of markup inside that tells the search engine like Google that do not follow the destination inside the link
Do follow links are crawl able and they count in back link also and No follow link cannot be crawled by Google bots. They are not valuable in your back links