Backlinks are the lifeblood of your SEO, but to get quality ones, you need to focus on good content. If you publish great content, you will get the backlinks you need. Yes, it will take time, but that's the best way to do it. Links that you buy/trade for are not nearly as valuable as the ones generated by good 'ol fashioned quality content. To the search engines, quality backlinks are like votes...the more you have, the more popular you are considered, and the higher your ranking will be. If you have content that others genuinely find informative and interesting (and WANT to link to), you're more likely to get the 'votes'.