When you are developing you will want the following:
Development Package - This has everything you need to set up plus some development tools and plugins that might make your life easier.
.Net Package - This gives you some additional .Net specific functionality and plugins. You need this in addition to the Development Package.
JQuery Package - If you want a JQuery enabled functionality you can load this. Like the .Net Package, this is an addon to the Development Package.
Compressor .Net - You will want this to zip all of the javascript files into a single file for faster streaming. This is optional but it is good to think about because TinyMCE creates a lot of javascript loading activies.
When you go to production you might want to consider switching out Development Package for Main Package, which is smaller and more compact but without all of the development addons for debugging purposes.
Good luck!