You have lots and lots of time to better invest time, effort, $$ in your self and to practice using the fine equipment you currently have. I speak from experience.
At one time, I would try to think ahead to my travels and what new piece of gear would make my work more unique or better. One year, I had overflowing pockets and indulged myself... Much became dead weight that I now had to schlepp along in my journey and a burden physically that when I had another issue, had to deal with the bulk/weight that would have been better left at home. Though I did use some of this specialized equipment along the way, it really wasn't necessary...
As I get older, it's going to be that much more impractical to bring the closet with me and so I think what will be reliable, smaller/lighter and get me the best quality overall. What I finally did to help analyze my shooting style is to dig into the metadata and see what lenses/focal length lenses and bodies that created my favorite/best work. By mining the data, I was able to focus on the tools that got me my best work and it wasn't necessarily the longest or exotic lenses. FWIW, your results will mostly be quite different than my work and my style. Also, since this sounds like you may be traveling with a photo-centric group, considered the pool of lenses, etc., that may be in common supply with the rest of the group and your hosts/instructors.
The down and dirty way, of course, is to ask your trip leaders their recommendations and give them a ring/send email and see what may be the best basics to bring along.
As always, with a journey of this magnitude, it's tempting to bring along a companion to be a pack mule for you and bring it all along under the guise of the FOMO, but in reality after decades of shooting all over the west and many trips to eastern Europe, simple and svelte and ready for action without the burden of bringing too much along.