1. Organic traffic (lots of quality content + links to your websites - preferably on the right keywords).
2. Partnerships/affiliate programs - you partner with other service providers that offer services that complete yours: they send traffic your way and you send traffic their way.
Affiliate programs: you pay for traffic/leads/actions. Lots such programs exist.
3. 'Out of the box' - games, competitions, crazy PR/marketing stunts to get attention for free (lots of good examples online).
I've successfully helped over 350 entrepreneurs, startups and businesses, and I would be happy to help you once I know more about your business. After scheduling a call, please send me some background information so that I can prepare in advance - thus giving you maximum value for your money. Take a look at the great reviews I’ve received: https://clarity.fm/assafben-david