Some pointers in order of your request with some remarks, citations from the plugin description or own experience if applicable:
- for Gantt diagrams there are actually multiple choices (in total absence of own experience roughly in order of likelihood of usability):
- TracJsGanttPlugin by jsgantt, computed % completion, actively maintained
- GanttCalendarPlugin - manually set % completion, month view for tickets, maintained
- FlashGanttPlugin based on FusionCharts Free - just for milestones, not for tickets, seems unmaintained
- SchedulingToolsPlugin, early beta, definitely unmaintained
- GanttChartPlugin no dynamic, just YAML text block to Gantt markup processor, seems unmaintained
- ExcelDownloadPlugin - using this myself: works great, there's even i18n support on the way
- WhiteboardPlugin - not totally convinced here
More generally I recommend TracStatsPlugin to you for making a nice bundled view with navigation to sub-pages on topics (repo, ticket, wiki). It looks tidy and useful, and it has a responsive maintainer.