I've tried several galleries but none worked well immediately. The Very Simple Image Gallery works immediately. But on my website the browser jumps to the top of the page when selecting a new image. I’m using the ja_purity template.
I solved the problem by selecting temporarily another template and then return to ja_purity. Then the problem was solved. Maybe it's a Joomla bug.
This is the only good functioning menu I found, that allows dummy parent menu items. You can set if parent menu items must have a link or not (for instance to an article). Also, the sub menus stays folded out, as usual, as you wish. See it here
I wanted a content list for the article headers, like Wikipedia. This is a good plug-in and it works properly. The control and features are perfect. Of course there are always minor improvements to imagine but it is very useful as it is now.