probably to get serious you would need either a cs degree or a lot of real world experience doing development.
i would not recommend shit like drupal, sharepoint, or wordpress. those are pre-built systems, you want to start at the lower level.
personally i would recommend javascript, with a strong emphasis on jquery. then with that you also want to know how to use html and css to make the pages look pretty.
backend i'd recommend java or groovy. groovy is like shorthand java.
then you'd want to learn about database concepts. you can just go for any old mysql db, or if you want to try learning a nosql database, i'd recommend mongo because it stores documents in a form that is very close to what you will be using a lot in javascript (json).
one neat stack i'd like to mess with at some point if i ever have a project i want to start working on would be the MEAN stack. it's a really light weight primarily javascript stack, including server side.