While you have many options and marketing channels to test the viability of your idea, the most recommended is to do so through SEM, the paid search engine marketing of Google and Bing. And I will explain why.
Search Marketing is one of the most important channels to promote your product of service. In my experience, I have had very good results.
For example, in the Travel or Automotive sector, where purchases are meditated and the customer journey is long and less impulsive. But also in a vertical market like ticketing, where the search acts as the last touchpoint (buy tickets Rolling Stones).
One of the keys of this channel is the "intention of the user", a person who looks for something in Google or Bing is someone who has a need, someone who needs information but also a product or service. In the start-up universe, we say it has a "pain" and you may have the medicine.
Well…, now that we understand the importance of the Search channel, what is the difference between SEM and SEO?
The first one (SEM) are payment results that generally appear above the organic results and below. The second one (SEO) has several formats, although it occupies results in classic format, lately it also adopts special formats for mobile called Snippets. You have probably already seen them, carousels of photos or products, accordions of questions and answers, and others...
However, I mainly recommend you to do SEM first for a strategic reason. Time.
To validate an online idea you do not have much time, you have to do it fast. Because you have to confirm that your idea works as soon as possible, or otherwise have enough time to iterate and modify your product or service in order to find a better market fit
Faced with this argument, the SEO takes a long time, even more if your website is new, getting into the top positions in search engines organically can take months or even years. On the other hand, SEM is instantaneous. You create the advertisement, you publish it and you have immediate visibility in search engines.
One you have validated your idea, then the SEO gains value. Because if you have done the SEM campaigns correctly, you have surely found the best keywords, and those are the ones you have to try to position through long-term organic results. To consolidate your business you will surely need to make it more efficient and lower your cost of customer acquisition, and SEO is ideal for that since the cost of creating content is always lower than the cost of paying advertising.
But that is for another post.