There's no such thing as the best strategy.
First of all, you need to tell us more about the niche and your budget.
If you have no budget, it means you won't be able to use any paid promotions like email marketing, Google Ads, FB ads, etc.
If that's the case, then your best options are working on your website SEO and try to rank keywords on search engines which will get organic traffic. But it will take a lot of time.
Another option is to build a following on social media - Instagram, Facebook, Twitter, YouTube, etc. Once you have your followers, you can sell them anything that they're interested in.
I have found great results from TV marketing actually. I'm reaching 220 Million homes (US mainly) and the traffic is mind boggling. Depending on the channel's niche, if you match it up precisely, you can really hit pay dirt. This isn't a cheap method by far, but it produces quite a few benefits like sales, website visitors, interaction potential, email list building to name a few. And what makes this better than paid ads is that paid ads are limited (metered) to your budget while the TV channel exposure has the potential of reaching massive (unmetered) traffic and produce unlimited results without adding to your budget or being limited by it.
Give new products a go, for example SaaS affiliate programs as they offer new and innovative products and services that can only bought online and there is less competition in this relatively new space.
SaaS Affiliate programs also offer high recurrent percentage commissions and payable for lifetime, So lets take a customer that subscribes to a SaaS service paying US$50 per month and renews for a full year, that is US$600 in total revenues to the SaaS company and based on a 30% commission, you'd get US$180 in commissions for one year alone.