I would recommend starting with Stephen Few's books: Show Me the Numbers and Information Dashboard Design: Displaying Data for At-a-Glance Monitoring to get an idea of visualization from a business needs perspective. These are easy reads.

Few is heavily influenced (and cites) Edward Tufte - Tufte is probably the definitive reference for communicating data with visual techniques. If you are interested in pursuing scientific visualization, you probably need to spend some time with Tufte. I never have properly done this myself.

These sources will give you a solid foundation without being tied to specific tech. You'll probably find lots of libraries built on top of d3.js that implement the basic ideas of both authors. I have been meaning to look at data exploration examples (e.g., stuff with visualization examples in R) and translate to different front/backend. That might be neat too.

Build some examples where the visualization provides real insight to a defined business problem and you will probably score some new opportunities for yourself.

Good luck.