Every one gets tired of building backlinks from time to time. And sometimes we get so tired we just quit. But many people forget, the most important sphere of ranking is on-site optimization. If you have built a site, and believe you have done so to SEO standards, you should rank in the top 50 pages of Google without one single backlink. After you have accomplished that section. The next is to move into your social media with google +, facebook, twitter and so forth. Dont forget to include these on your site and also to ping them every time you make a post. And get followers. After you have completed this stage, don't buy backlinks, do them yourself, and find good quality sites and discussion forums to talk about your market. YES, it is WORK, but just one quality backlink per day for each of your top keywords. This method will always work, you will never get penalized. But remember when you build links.
The few above are just an idea amount of percentage needed. The above is only for SEO. SEO alone will not bring you in traffic. After you see yourself start to rank, move into social marketing. This will be the kicker that gets you to the top.