Before You start installing plugins, it's a good idea to consider some things:
1. There is nobody who ensures that older plugins work proper with newer jEdit versions. The plugin maintainer would have to do so. But when a plugin is older than 3 - 4 years, chances are that this plugin is orphaned...
2. Most plugins don't come from the core developers. They are not coordinated! So, many plugins implement similar functionality, and You have to chose ... (I would prefer newer ones).
3. Some plugins use external programs that You need to install separately and tell it's path to the plugin via plugin options (i.e. ctags, global)
4. Every installed plugin noticeably extends the time jEdit needs to startup.

My advice is to begin from scratch:
Re-Install jEdit and install plugins that are some kind of core plugins like:
- ColumnRuler
- Console
- Error-List
- jDiff
- MacroManager
- ProjectViewer or Sessions
- SideKick
- SideKick parsers like:
- XML (recommended)
- JavaSidekick (if You want to edit Java source code)
- CtagsSidekick (only if You know that You need the external ctags)
- TextTools
- WhiteSpace

Then, after exploring all the given functionality and options, You can try further plugins. But install them one by one.