The best way to build up an online reputation is through the regular sharing of original content that provides benefit to others. Ideally, you will post every day, or even multiple times a day. Only through regular posting and sharing will you build up a library of stuff you have thought about and problems you have solved that others can see.
This habit of regular sharing has a couple of benefits. First, you might just provide a solution that can help someone else working on a similar problem. Also, you are showing what you can do to people who might have an interest in knowing more about you. An online portfolio of work that potential clients and employers can see is far superior than a resume or printed portfolio because it shows what you are working on right now (Kleon, 2014). If you can discipline yourself to make regular posts about the projects you are working on and problems you are solving, you are making yourself stand apart from the crowd.
Kleon, A. (2014). Show your work. New York, NY: Workman Publishing.