How to create a statistics dashboard of my users using Views?
Use the Charts module and its integration with the Views module. A straight forward cloning of the delivered views example would do what you are asking for. Have a look at this online example to get a first impression.

Some more examples of the Charts integration with Views, using data contained in "nodes" (so not using any Views aggregation facilities):


Single chart, not attached to a table, and without aggregation.
Table with attached charts, and without aggregation.
Combination chart without aggregation.


Disclosure: I'm a (co-)maintainer of Charts.