If you are looking at the cheapest method of getting traffic to your website, you should be writing articles. You need to write articles that are focused on the topic of your website with a link back to you, and submit them to the article directories, which make your articles available to the public. There is no cost to you to submit to these directories and you will get free traffic.
You can sign up with as many article directories as you care to submit articles to, the more the better. Getting your articles in front of as many people as possible would be your priority. When your articles are listed in the directories, you have the benefit of other website owners using your material on their websites which gives you even more exposure.
Then you have the search engines that will also pick up your article which will be found by people surfing the internet for information you have. You will need to learn how to use keywords to help the search engines get you indexed. Google would be the main search engine that would bring you traffic and if you can get on the first page according to your keywords you have the potential to get a lot of traffic.
If you really want to expand and speed up your article writing and submissions, you could use one of the article spinners and submitters. What this would do for you is allow you to take one article and convert it into many different versions. Then you could take all of those versions and automatically submit each one to a different article directory.
