the first part of the question is not clear to me.
The second part:
1) If you want an Expression to use the second axis on the right,
goto the "Axes" tab; select the expression you want to change; select "Right" in the "Position" frame
2) If you want to add symbols (dot, square, ...) to a line,
goto the "Expressions" tab; select the expression you want to change; select "Symbol" in the "Display options" frame
you can select different symbols from the dropdown list
you can change the size of the symbols and the thickness of lines under the "Presentation" tab
Thank you very much! This definitely solved my second question!
As for clearing up the first question
I need the gauge to look like this.
The part at the bottom which gives the margin amount, is a moveable object. I'm guessing its a text object which is somehow linked to the data.