1. Pay for it (ads)
2. Borrow it (distribution agreement with a third party, who has an audience)
3. Build it (organic/SEO, use your own audience that you started building years ago)
That's it. Every other way is either a hybrid of two of those (e.g. paying someone to email their big list) or is one of them deeper down. So it sounds like you don't have an audience, which makes #3 impossible. At this point you can either talk to a friend or business associate who has a good-sized list, and see if you can come to some sort of an agreement with them, you can pay for ads on a relevant platform or blog, or you can start building your list now.
Is your landing page for a [free] lead magnet, or a purchase? Purchases in the impulse buy range ($27-47, but for developers maybe up to $97) get you qualified traffic, and for really good sales copy can be more-or-less self-liquidation, e.g. you are earning in net revenue basically what you're spending on ads. But often times it's just to take the edge off the ad spend and make sure your list is super-qualified people, since they've already paid you money they're more likely to pay you more.
My email is in my profile and I'm happy to give you an unbiased opinion of your landing page - I have nothing to sell you, it would just be what I think of the copy, offer, design, etc.