how important is NO FOLLOW links in our sEO?

yes i am agree with you. mixer of dofollow and nofollow shows google natural method of linkbuilding which means More Ranking strenth in google results.

There is a LOT more fiction to this statement than fact. Honestly, this "need" to have dofollow and nofollow links is totally without basis. Personally I think it was created by SEOs to justify them building easy to find links with comment spamming that are totally worthless from an SEO perspective. They drive traffic... but that's about it. It's a phenomenon that has grown out of "unnatural" link building techniques like blog comment spamming.

If you think about it, a legitimate web site with ALL "natural" backlinks (I mean links that are freely given from other webmasters without the site having to ask for the backlink because they view the site as some authority or as a useful resource to their own site's visitors) could very well have thousands of followed links with absolutely ZERO NOFOLLOW links. Natural links VERY rarely are NOFOLLOW links. In other words, sites that have NEVER built links themselves or hired anyone to build links for them could very well have ZERO NOFOLLOW links in their back link profile.

Do your REALLY think Google is going to somehow penalize a site because they do not have NOFOLLOW links? Hell no... Actually, if Google could have it their way, this would be their Eutopia... That ALL links on the web would be natural links, given freely as non-biased votes for URLs with great content...

The sites that have NOFOLLOW links are the ones that are using "unnatural" link building techniques. It's the sites where the site's webmaster (or someone they pay) "plants" links on other sites that allow user generated content (UGC) like blogs, forums, article submissions sites, directories, etc.

Because these UGC sites are not always moderated and don't always know who is going to be posting content on their site, they frequently NOFOLLOW those links so that their site won't be penalized for promoting a bad neighborhood site should someone drop a link on their site pointing to a site later determined by Google to be a bad neighborhood site.

If you want to build NOFOLLOW links, do it for the traffic. But don't try to play it off as something that is "necessary" for a back link profile to look "natural". If you were worried about that, you shouldn't be building links using "unnatural" techniquest to begin with.

Very few percentage of links on the internet are actually no follow.

I wouldn't worry about going out of your way to get them at all.