You simply have to learn and implement till you find something that works for you. Others are good with SEO while others simply rely on Pay Per Click advertising or social media marketing. Always remember that there's no best way to market online, you simply choose something and make it work.
Most online marketing strategies (if not all) do work when used the right way with a positive mindset and heart of a warrior (never give up). One thing I can promise you is that, it's not going to be easy, it's like learning how to ride a bike for the first time. You'll fall a couple of times but get it right if you keep trying and have a positive mindset.
Same with marketing, don't let a few failures bring you down, simply keep learning and implement what you learn. When you take action then you'll most likely get positive results and positive results increase your faith, the more faith you have, the more action you take and you keep getting great results in return.
So, I guess the easiest way to master online marketing is to get started
