First I will want to know what it is you want to achieve. The internet is not and never has been a one size fits all arena, and it still amazes me that everyone I meet has a different take on how to make money from the internet.
So you presence will probably start with a website. If it does, the most important first question is what is the site for and how are you planning on getting customers to it?
If you are looking for paid traffic only, then the look of the landing page is everything, however if you are relying on organic ranking for some traffic the most important part is not how good it looks (sorry designers) its the site structure. Does Google like the structure, or is it difficult for Google to spider. (Get round). Because until you can get people to the site, you have no hope in converting them.
Again depending on your business, you might get a lot of customers through Linkedin, Facebook, or other social media. These are all key parts of a successful Online Presence.