Have you not got any access to any real time data?
Start off with using one of the mango internal points. A virtual point will only be updated if you manually set it or use a meta datasource point or a scripted datasource to populate it.

Let's use system uptime to start.

<ma-point-values point="pt" point-xid="internal_mango_uptime_hrs" values="val" rollup="NONE" latest="100"></ma-point-values> <ma-serial-chart series-1-values="val" series-1-point="pt" legend="true" style="min-height:300px;" ></ma-serial-chart>

You need to have enough history on a point to actually display a chart.
EDIT: missed a few attributes.
Secondly: Show your code, and are you actually using the brewers dashboard? This seems a better fit under asking for user help. I think this needs to be moved.