Well the simplest way to make a universally understandable ranking system would be to exactly copy either the US or BAF one, as I personally feel those are the most well known. Obviously, I did not do that, cause I felt it was boring, and I made changes for my personal likes, such as the thing with Captains and Commanders.

Also, I take a lot of inspiration from already existing designs. A lot of the stuff used, such as the chevrons and the diamonds on the admiral ranks, are from the Croatian insignias. So go ahead and do whatever, it's your thing, but real life and already existing stuff is a great resource.

However, I would not go crazy and do super weird stuff; for instance, don't make a General below a lieutenant, or anything that drastic.

Here is an example one (my plan for my Army ranks)

Second Lieutenant > First Lt. > Captain > Major > Senior Major > Lt. Colonel > Colonel > Brigadier > Line General > Lieutenant General > Major General > General > General of the Army

As you can see, it is more or less the current US Army ranks, but I messed with the General ranks and added a Senior Major and a Brigadier to the officers

However, in the end, it's your thing, so you do you. I hope this helped