What kind of contacts will I need to have to register a .Gr .COM domain name?
You will need three contacts: an Administrative Contact, a Technical Contact, and a Billing Contact.
Please note that it is also possible to use one contact for all above
Can I count myself as one of the contacts?
Yes.
Most people are in fact, the Billing Contact. 101Domain recommmends utilizing two other sources for the Administrative and Technical contacts.