Hi Radhakrishna,
What I understand from your query is that you want 4 different types of report charts in a single dashboard and also you want to add some custom fields of user object. So first of all you have to create a Custom Report Type between opportunity and user object.
Then you can either create a single report using that custom report type with all your fields and filter and you can fun around with summarise and grouping functionality over different fields. And use a single report in a single dashboard with four different components/charts.
OR
You can create four different reports using the custom report type with your custom fields and filter and then create a dashboard with its four charts and display as per your need.
Hope this will help you.