Make a contrast between the three main buttons to the background. As you can see, the colour of the MINIGAMES box is only a slightly darker blue than the background, it just looks too mixed up. I suggest trying to put shadows or outlines around the buttons, or maybe experiment with new colour palettes as @Elttob has suggested.
Look what happens if you could add a title somewhere on top there, it might be visually good looking. Remember, if this is a menu, you want to leave a good impression to new players, so there’s a higher chance for them to come back. The background can even be replaced with something more unique and aesthetically pleasing. I would try with gradients or some images/thumbnails that reflects your game.
The following image, for example, can be used to replace your bland-looking background.
If you want to do something more advanced, consider using Tweening and animations. Other than that, the shopping/settings bar down the bottom left corner seems to obstruct the whole point of a main menu. It looks annoying to me, so perhaps you can move it somewhere else.
A question for you, how satisfied are you with your current UI layout? Is there any specific thing you’re aiming for?
I think you could at least keep the theme the colour scheme you have with two of those icons to the settings icon.
With the bottom UI, you add a shadow but you don’ do the same for the other buttons. It looks pretty left out, you should make it consistent throughout your other buttons. But personally, I think there shouldn’t be a shadow there at all.
Nevertheless, good changes.
