This is a very broad question.
But what I can say is that no matter what way of online promotion and marketing you choose there always going to be some costs involved even if you do everything yourself.
Three main ways are:
- Paid advertising
- Social media marketing
Paid advertising could cost anywhere from 0.01 cents per click or view, to a couple of hundreds of dollars per click. All depends on the targeting and the quality of traffic, and industry.
Similar for SEO, the easy to attained organic traffic is usually low quality or worthless, and good quality of traffic costs some time, money, and effort to get, meaning that those keywords will be much harder to rank on the first page because there is a competition.
Social media marketing is a great way to get your content viral and engage the audience with a lot of social proof which is important in terms of business and conversions. But again, you need a gig following fan base which takes time or money to build.
Besides SEO, what are other tips to gain more exposure?
There are many various marketing strategies that could be viewed as a single separated strategy, but often also could be defined as a part of the overall SEO marketing campaign:
Social media marketing