Why is my dashboard showing 503 errors? Is this a host issue or a civi config issue?
Some issues with the dashboard have been fixed in the upcoming 4.7.11 release. See CRM-16035: Dashlet refresh can crash server / Replace use of HTTP_Request and CRM-17663: Dashlet code improvements for details.

There are quite a few existing questions on dashboard issues on this site - you'll find some good answers there I'm sure for dealing with CiviCRM below 4.7.11. 


The dashboard does not render
CiviCRM Dashboard Not Working - WordPress installation
Dashboard problem after installing reverse proxy server
CiviCRM Dashboard Hangs for 5+ minutes


Once 4.7.11 releases, that should resolve your problem.