Tetris brick menu

Hi,
Im beginner in Unity and in the C++ so please be patience .
I do 3DCG almost 15years but the visualizations start boring me so i want try something else and i pick AR and even make some : https://play.google.com/store/apps/details?id=com.Whitekanga.IKMSv1
Now I’m planing to get rich;) and trying to make some great AR but i need menu/inventory thing.
I watch on youtube 10 inventory tutorials but they are more complicated i need simple one.
Remember Tetris You always see 3-4 next bricks and thats what i need.
Tetris alike menu.

1 - I need 5 GUI.Box (Austin Gregory tutorial easy)
2 - I can click only on the first one (Austin Gregory tutorial easy if slot*=0&& mousedown etc )*
3 - I need to fill those empty slots with the brick List lets say 50 of them in ID order ( no idea )
4 - When i click on first bricks I remove it, and the rest move by one ( no Idea )
4a - The GUI.Box ID order : 0,1,2,3,4 click 1,2,3,4,5, click 2,3,4,5,6 etc
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Thanks for taking time to look on this in advance.

I make some script but im not happy with it.
App looks like this on Android 2,3 version. :

https://vimeo.com/135333206