A mockup for an RPG I’ve had in mind; most action is in the middle of the screen, so it’s important for UI elements to be surrounding the border in a rectangular or circular formation.
I personally find it better to have fairly simple shapes and colors for visual clarity (with some flourishes), then using animation to give those elements personality. I am personally a fan of using rounded (softer) shapes to compose a UI, to allow for a design that is easier for eyes to follow - at least, in my opinion.

In this example, there are many individually moving parts following different timings and patterns from one another to accommodate for the relatively simple images. By combining multiple of these at once, we can generate a full-bodied effect.

As a closer look at the Player UI from the battle transition above, here is the entrance animation for an individual character. Utilizing squash-and-stretch and other subtle flourishes like the click-in of the resource bars, this UI element feels less stiff.

Every element that is a player resource that they pay attention to is colored vibrantly in contrast to the monochrome backgrounds that they are laid upon. This is to make them obvious in their movements and when modifications occur due to gameplay. Each piece also has a slight gradient to accentuate fills and rotations.

This title + menu mockup was created to invoke the feeling of game menus from the early 2000s, with PlayStation 2 RPGs in particular. As such, the formatting of menus is very “classic”.

Due to preference, I still used simple rounded rectangles for multiple elements. However, due to the visual complexity of the background in both menus, it was better for the elements that the player would have their eyes on be less visually complex in comparison.

Within the in-game menu mockup, each menu option is given their own icon in addition to text to reinforce concepts and allow for easier navigation.

Another important factor of making these menus clear to use is the help bar that is at the bottom of the screen at all times; this not only tells players exactly what they’re looking at, but also gives them the controls to be using in a particular menu or submenu.