The visitor will come to your site, whether you promote or not. But the number will not be bigger if you promote using the ads on Google, Bing, Yahoo. But that will need some monthly budget. I prefer to do it by free using an article because that will be more powerful to attract more visitors.
Besides that, you need to check your template and links to your site because that can be your backlinks and that can give you more power to have a good list position on the search engine. Many others you need to learn about SEO and I suggest not try with the blackhat because that can make your site delisted from the search engine. The worst is your site will be ban from Google.
SEO rules change almost daily. Writing and posting solid articles is not enough. No matter how good it is, a regular article update will always be positively used for a better SEO rank.
Using ads on any search engine service does not work strictly in the SEO service. It will increase traffic, bring some leads, sales but has no significant direct impact on SEO. If that were the case, the richest would buy ads and not hire SEO experts.
About blackhat methods, they can only be used for short-term businesses. For example, someone wants to resell ticked for Olympic games and needs to be visible only during the duration of the event. Who cares if there is a penalty by Google after everything is over and the need for that website ceases.