Hi Tony, .net core is still very young and not used much in current CRM projects due to certain limitations
However with the introduction of the Webapi, there will be less reliance on .net in the future, meaning crm development will become more easier fro the wider developer community
MVC is still a very popular framework for delivering custom wep application Integrations / portals based in .net
any certifications for C# will be extremely usefull for developing your plugins and Webservices / WCF as well as Visual Studio along with TFS is very important so you can check in code and collaborate with other developers. Some common examples of development in CRM involve the following;
Windows Communication Foundation (WCF) web services•Describe integration of Microsoft Dynamics CRM and WCF; describe how to handle WCF faults; use and specify Open Data Protocol (OData) elements when querying Microsoft Dynamics CRM data
QueryExpression, QueryByAttribute, LINQ queries and filtered views; explain how to save queries; explain FetchXML and custom SQL Server Reporting Services (SSRS) reporting in relation to Microsoft Dynamics CRM; describe the integration of Microsoft Azure with Microsoft Dynamics CRM
use the Execute() method, use entity-specific and non-entity specific requests, use simple generic request messages; pass optional parameters in messages
use of JavaScript libraries to customise Microsoft Dynamics CRM; describe form and field events, including OnChange, OnLoad, OnSave, TabStateChange and OnReadyStateComplete; implement IFRAMES in entity forms
Implement JavaScript for client-side events, debug client-side code, request external data, pass parameters, access Microsoft Dynamics CRM 2013 web services. implement the Xrm.Page object, implement Xrm.Utility, explain how to test form types, describe the form event handler execution context
set dependencies and pass parameters, define the allowed query string parameters, add and handle form parameters, explain the getQueryStringParameters method
use the different types of web resources•Define webpage (HTML), style sheet (CSS), script (JavaScript), data (XML), images (PNG, JPG, GIF, ICO), Silverlight (XAP) and style sheet (XSL) web resources; create web resources; identify the limitations of each web resource; implement the passing of parameters between web resources; reference web resources; implement JavaScript libraries for code reuse across multiple applications
use REST, OData and JSON in Microsoft Dynamics CRM•Explain Representational State Transfer (REST); use EST in AJAX and JavaScript, explain JavaScript Object Notation (JSON), explain how to use the XMLHttpRequest object, use OData and JavaScript to create and update an account record
Explain how to use JQuery in Microsoft Dynamics CRM•Explain JQuery and how to use the JQuery object, use JQuery with a web resource, use JQuery to interact with the CRM form
CRM Onpremise may require some SQL, However Powershell is something I highly recommend as its becoming more and more usefull for automating crm deployments
Hope that helps?