Because R is a free software environment, there are many fantastic, free resources to help you learn more! If you are ever trying to do something in RStudio, try giving it a Google search. You'll likely find many sites with helpful tips to share!
Here are some online resources to get you started:
RStudio ggplot Cheat Sheet: a very full sheet of ggplot functions and aesthetics. Also shows which visualizations make sense with discrete or continuous variable combinations.
Stack Overflow: a place where people ask and answer questions about many things, including ggplot2.
R for Data Science: a whole ebook for in-depth explanations of ggplot functions and data wrangling in R.