Use c#/.net to get crm data and dump to xml

Hello.  I work on a team that supports CRM 365 in IFD and I'm interested in developing a tool that can get specific data from an organization and write it to an xml file.  I understand that I can either use the OrganizationService or the WebAPI but was hoping someone could point me in the direction to get started on a project like this.  Thank you kindly.