You can’t give services a priority upon startup. About all you can do is set service dependencies. You can tell a service not to start until another service has already started. The downside to this is if the service that another service is dependant on is restarted then both services are restarted in order.
I talk about how to do this over on tek-tips.com in an FAQ called “Stopping other Services from starting until SQL Server is running“. The FAQ is based on the SQL Server service, but the technique will work for any service installed on the machine.