Is there any other ways I can get qualitative link building for my site apart from blog commenting, directory submission and forum posting.
Yes, providing they are relevant to your site, for example if your site's niche is shoes, you need links from shoe and fashion related blogs, forums etc, this way it adds authority to your site.
A great way to get quality links it to contact other sites and offer to write an article or some form of content for their site. In exchange for your article they give you a link back to your site. It is called guest posting and can get you some really nice links from high pr pages. Although, it is a bit time consuming the links are totally worth the effort.
What a quality link building is actually the back links of your Niche( Same PR, Same theme, Etc),, Article syndication, blog syndication, Social Bookmarking is the best way to get the quality backlinks.
If your site has good quality you may get backlinks in natural way. Make interesting content with attractive titles. Titles must interest your visitors so they woudn't close your site and began to read. Posts with tutorials, reviews, tricks with a lot of images and videos earn a lot of backlinks. Such articles couldn't be written in 10-20 minutes, you must put in them yourself.
Quality of backlinks is to do with the site trust and authority, not the type of site (blog, forum etc.) Free ways to get quality links is to find best perfroming sites in your niche and appoach their webmasters with a request for guest post and/or link exchange. Most will probably reject you, but another way to do it is to analyse your competitors backlinks and do the same with them. However, if you have a budget, even if a small one, I highly recommend to automate your link building with the most trustworthy link building services. That would be the best investment you can possibly make. Check my sig for reviews.
Make sure you use relevant/unique content. Engage in social media, post on forums, blogs, videos, etc.
bought links but I got no concrete result. I enrolled in several social networking and all no effect.