Not A Good Idea: This example shows a chart with different fonts and font sizes together with a harsh gridline that makes it distracting and disrupting. The design pulls the eye away from the information the chart is attempting to show.
A Good Idea: Here an approach where less is more would be a better idea in an attempt to follow visual hierarchy to guide the eye to the most important parts of the charts, the data. There are many clever things you can do, that when combined, can improve to clearly show important parts of the chart. These include clever usage of color, symbols, notes, font color and size.
Soften the font color and minimize the font size used in the left and bottom axis. Then soften the grid lines in order to push it all to the background. Finally increase the font size used on the line labels above each data point and add a line symbol such as a a circle. Together this will emphasize the data points of the line and as a result will guide the eye to the right part of the chart.
For more styling recommendations, see related blog post Less is more.
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