"Creativity is just connecting things. When you ask creative people how they did something, they feel a little guilty because they didn't really do it, they just saw something." - Steve Jobs
One of the first lessons I had in data visualization was comprable to a lesson I received from photography: Learn from what you love.
By looking at the work of others you can quickly identify aspects of design that you are attracted to and that work for you. Don't be limited by deliverables created in your product of choice (Tableau, Power BI, Spotfire, etc.). Just ask questions: what does their viz accomplish? How can I do that in my software of choice? What aspects of their dashboard do I like? What is it about those details that I like?