Thanks for the clarification. The very first sentence in the jam page reads:

… build a game during the month of November.

That’s why I added this comment.

Maybe you can update the submission entry to clarify how it relates to the theme of “waves”?

Thanks for taking the time to consider my comments :)

There is a clear improvement on UX with this new version, it is crazy how some tiny tweaks can make a huge difference. The cost of building is now obvious and hiding the "ask to surrender" button was a great idea.

For overall UI improvement I can suggest you to define some hover/pressed states to your buttons and to change the cursor shape when the mouse hover a clickable element. This helps a lot users to understand what is clickable and what is not. You can also have a "disabled" state that clearly indicate that this is a button which is not clickable yet. For this there is an easy path which is just to have a few different colors for the different states, for example lighter when the mouse hover it, darker when you the mouse button is down, and grayer when the button is disabled. It adds some interactivity so when you hover buttons as a player you can quickly see what changes color and what does not and thus intuitively feel what you can interact with or not. A more advance technic that I like to use in my own creations is to blend between the different button states using a simple lerp animation, like scaling the button to be bigger when you hover it and shrinking when you click it and blending between colors, or even having some animation on the shape, icon, etc. A hard color swap is a must have but those more advanced animation technics, if done with subtilty, makes everything feel more polished and intentional. There are also a lot of design technic regarding affordance of interacting elements, which means "make the think that should be interactive looks like you would be able to interact with it in real life", a classic is to make button with a subtile 3d effect with shadows and lighting that change depending on the button state. You can find a tone of resource about that on the web if you look for interface design in web programming, they looove those kind of stuff ^^ 

Another UX improvement that could be an easy fix is to make the panels closable on click also if you press outside the panel. And you could add some darkening overlay behind the panel to clearly show to the player that this is an overlay and that what is happening in background can be discarded while the panel is open. Being able to click outside to close is a good way to give some flexibility to the user, he/she can be sloppy and it still close things properly. I think a good advice for those UI/UX improvement is to try to think about the intent of the user, to predict what he/she would want to do, and allow some flexibility in the response by doing it even if the user did not input properly.

A quick note on the battle result, the state change before the animation title screen appears which allows the player to see the result of the battle for a few frame before the full screen goes to black. I don't know how you deal with it in code so I can't give you an exact fix but in general it is something in the direction of "wait for after or in the middle of the transition animation to update the game state", or "add some timer to delay the ui change of half the battle screen animation duration" (the later being more a hack than a fix but players don't see your code so do not feel bad about cheating like that, after-all, a game is just a huge magic trick xD)

I am not that good with audio effects either and fortunately I found someone to help me with that. But for the few games I made without having a dedicated person for that what I usually did was a mix of finding free assets onlines and creating some of my own (even if it is crappy) by kitbashing and making weird noises in a microphone. If you have zero experience with audio creation I would suggest you to just find some stuff online. There are a lot of free resources available and you can go far with just this technic. Then the next step is to put your hand on Audacity (or similar) to be able to quickly edit those if needed (e.g. cutting bits, shortening things, etc), I don't believe that I know more than 1% of the software capabilities, but it is plenty for doing some basic stuff. And if you want to try to do some assets yourself then I suggest to use Audacity too, records a bunch of noises together with a microphone (your phone is enough), and just slap them together in Audacity until you have something you like.

Don't tell my audio engineer that I told you that, but from my experience, even crappy sfx when put together and tweaked a bit can sounds great in game. You don't need to have impressive sfx, even very simple ones will make a huge difference compared to no sfx. Then if you can find/make/afford some nice sfx it obviously adds to the quality. But the step from "none" to "crappy sfx" is way higher than from "crappy" to "polished"  (in my opinion ^^, but I am more a visual guy than an audio guy, so it may be irrelevant). 

You can also find plenty of resource online about audio engineer that shows how to make sfx. They have some crazy technical vocabulary so finding a "tuto" may not be ideal, but I found it very useful to see how peoples layer things together to make sfx and then try to do the same with my basic audacity skills. As always, you don't need to master it to be able to make things :)

Regarding the usages of sfx in your game, obvious ones are on clickable element, but you already have a bunch which is great. You could also have something on mouse hover to emphasis even more the clickable state of buttons. You can have some noise when panels show, screen change. Some battle sound when a battle start. Battle win/lose sfx. Some army walking sound when your army is moving. Etc... 

I hope this will help, good job on the update :)