Much like the budget, there is no clear-cut answer to this question. It depends highly on your business and who you are looking to target. There are hundreds of digital advertising platforms, but by choosing the platform that is best fit for your audience you can see improved results. The easiest way to determine which platform is best for you is by asking the question: “Where does your audience find your competitors?”.
For example, if you are marketing a B2B SaaS product then it’s likely you can catch your buyer at a time of purchase intent while they are browsing LinkedIn. Yelp, on the other hand, would not be the best time to put your product in front of them.
Alternatively, a company looking to sell marketing materials and signage to franchisees might choose to target customers on Facebook, which would allow them to target individuals by age, occupation, and interests. A targeting filter that might be interesting to this type of company would be individuals interested in franchising or perhaps Quick Service Restaurant Magazine.
Ultimately, you should be able to apply learnings from one platform to another (as well as your overall marketing strategy) as you continue to iterate and define your target persona.