What version of RapidWeaver do you have installed?
To answer your question regarding what else do you have to buy… Nothing, works out of the box. If you want more functionality, the first thing to buy is Stacks by YourHead Software. You can buy Themes, further functionality with third party stacks (Stacks by YourHead is the manager of stacks), plugin page types for a cart or form manager or various other things as you need them.
RE: dragging in photo’s and only getting the url inserted is likely because you chose HTML page type or Markdown Page type instead of Stylized page type.
Some of the video’s are RW 5.x and some are RW 6.x (Current version is 6.3.7), there are definite layout differences between the two versions but the functionality is basically the same. If a video has not been updated to RW6 then it is likely because the functionality is the same between 5 and 6.
@joeworkman and @1LittleDesigner (Visual guide) have ebooks for RW 5.x that mostly apply to RW6 which I would recommend for the beginner (one is $5, the other $9 so cheap investment unless you want the hard copy).