The best types of backlinks are those which real humans use. Increasing your traffic is what the bottom line of all website promotion is. It is not about getting rankings, that is just a step toward getting more traffic.
A few years ago good trainers and mentors were teaching people to be as independent of search engines as possible, remember the internet existed for a long time before search engines. Google is a perfidious lover and what you have today may be taken away tomorrow, but traffic bearing links tend to stay around for a long time.
Given that we know that search engines reward sites with an appropriately large number of incoming links with improved rankings it makes sense to build links for the purpose of improved search rankings but the trick is to seek out the traffic sources. Just as a point of reference, I used to run a site with something north of 4000 daily uniques, over 70% of traffic came from sources other than organic search (and I never, ever, bought a visitor)
Where to find the links? This will vary according to your niche. For some niches it might be that you see a lot of blog traffic, for others it might be from one or more forums. Some article directories are great for this, they get lots of readers of their content. If you can get a decent article written for less than $5 and over the course of 6 months it generates traffic from one directory that spends $15 then that single link has been well worthwhile.
One way to find traffic sources is to look at the link profiles of sites that are ranked well, sites that you can respect - not rubbish, see where their linking is from. I bet that you will find traffic sources by looking at what your competitors' webmaster and marketing team are up to.