I am new to K2, and had downloaded K2 extensions. When setting up an item, I find that to insert a gallery I cannot use any of the extensions I have found, but only Simple Image Gallery Pro. This is true for the video. Am I missing something or do I need to purchase these products first?

 

 

Allvideos and Simple Image Gallery Pro are both on the joomlaworks website.
Allvideos is a free extension
SIG pro comes in two flavors, free and pro, Save yourself a lot of headach and hacking and purchase sigpro, as it usually works right from the install.
K2 supports item images, but in order associate a gallery to an item you will need sig
Sig will work from being associated with a k2 item or just like other extensions with a { gallery = asdfasdf } type of syntax anywhere in joomla once installed (check syntax)