Hi Frank, thanks for trying the Bubble chart. For bubble charts, X axis, Y axis and Bubble size are metrics usually for showing performance, and Category field is for splitting the full dataset into different bubbles for each unique value for that field.
I just made a simple example for Bubble chart, like below.
This chart is analyzing advertisement performance. it shows the relationship between Reach (Y-axis), Engagement(X-axis) and CPC(Bubble size). Each bubble is an age group, so you can understand the performance of each age group. you can also change the age group to Ad groups, Campaigns etc.
For your situation, maybe you can try to put the Age into Category, and leave the Revenue and Number of prior_orders at Y-axis and X-axis, by this you can know the performance of each age group.