Whether you have one variable or, maybe, two you can find a visualization that might help get your point across to your audience.
The visualization you choose is up to how many variables you want to show, what you are trying to show, and how you want to show it. You should be flexible to change your target visualization to get the best response in the end from your audience. Websites to help aid you are The Data Visualization Catalogue and From Data to Viz.
Breakdown of resources:
The Data Visualization Catalogue
- best if you have an idea and want to confirm how it is used
- gives an example graph
- has a list of what programs you can use to make the graph
From Data to Viz
- best if you have no idea what to pick
- gives common mistakes for each type of graph
- has a understandable visual to help you pick a graph
This visual to help you choose a chart it is sorted by what you want to show and characteristics of your variables

Credit: Andrew V. Abela (The Extreme Presentation™ Method Creator)