Hello, I think you should have asked first instead for what platform gives the best ROI. More specifically for what purpose?

Is not just about saving money, what about your time? Do you have the right concept in place so that you're not interrupting viewer's time with random ads that they are not interested in? Potentially costing you sales rather than driving them.

For example if you are promoting a new beard oil for hipsters, you are probably better off shying away from FB. While Instagram or Twitter might be better for ROI.

Reddit, hmm...it is a SaaS? otherwise maybe not so much.

For example,I marketed a pair of crotchless shorts for outdoor enthusiasts. Particularly females.Anyway for this product, a combination of paid google searches, instagram and facebook proved to be a great combination.

The ads, however pointed to custom landing pages I created with A/B testing to see what worked best. Tweaked as needed and re-ran. We went from 0 to over 9,000 monthly visits after creating a brand new domain for it w/ zero prior SEO.

In Phoenix, my wife is the owner of Honest Maids. I started off the marketing for this the same way. But I used Instagram, facebook and business cards customized for events and each with a unique purpose link. - to a landing page. Instead of waiting the typical 3-4 month wait for clients to call in for services I did it in less than a month.

For our marketing and web design team I use a combination that includes Linkedin, Craigslist, Quora, Twitter, Referral systems and blogs' backlinks.

(obviously me answering here for you is another way of adversiting something for me...)

It all depends on where your clients are... follow them not the price to advertise there ;)