Where to go from here
At this point you should feel quite confortable with Mvc Controls Toolkit controls.
Just play with all live examples, read the code and explanations they have and explore the full documentation starting from the concepts and classes encountered in these examples.
Try also the complete tutorial on dotnetcurry and download the associated VS 2017 project.
There you will build a complete ASP.NET MVC Core web application from the DB layer to the UI and you will show data from a database in a paged Grid with filtering/sorting/grouping and add/edit/delete capabilities.