Everything depends on the business itself. Which sector? Which customer are you trying to reach?
I think these days advertising through TV or radio is outdated. Yes it's still done a lot and important for a lot of companies but this is not useful for small to medium size businesses.
Digital marketing is the way to go now. Anyone is capable of doing this and you don't need a lot of funding too. Facebook, Instagram, Twitter, Google,.... so much opportunities. The key is to execute it perfectly in order to gain from this strategy. It's like maintaining a blog. At first you get close to zero viewers and zero response. You have to be patient, have a good plan and be consistent with the content you're writing. It will take time to gain a loyal following. A mistake a lot of companies do, is that they have multiple social accounts but post the same thing on all of them. The same article on Facebook, Instagram, ... . Remember creativity is a valuable aspect within the business environment. Try being creative with the marketing factor of a business. Maybe you could post everything that is related to your product on Facebook and everything that is related to the daily work situation on Instagram (fun pics of the staff, etc.). I think the most important part about digital marketing is to figure out on how to build a community for your product.
Of course marketing is much more than advertisement. It's your product and knowing who your customer is. You have to ask yourself why you are doing this. Why do you want tot start your business? It is not important what your product or service is, it's important that you create a certain feeling. Emotions are much more valuable than logic. Just take a look at the TED talk of Simon Sinek.