How would I make a case clicker system that displays rap combined of all items?

just to answer you and help you out a little i made a example script. the script gets 2 values from the character and adds then together and displays them on a gui.

local plr = game.Players.LocalPlayer -- getting player
local char = plr.Character -- getting character
local ui = script.Parent.TextLabel -- the textlabel
local item = char.Item --the first item
local value = item.Worth.Value -- the items value
local item2 = char.Item -- second item
local value2 = item2.Worth.Value -- second items value

ui.Text = "RAP:"..(value + value2) -- adding the values together and displaying them

because i wasn't given enough information i just made this as a example so your friend could understand it a little and try to come up with something himself. i would have created a table but i dont know what you would call your items by their name but i would suggest making a folder inside the character with the items. i suggest your friend also learn lua a little before he tries making a game. some things he can do to learn lua are: watching yt tutorials, looking at answered questions on scripting helpers, exploring on devform or theres even a game that acts as a tutorial to teach lua.

anyway i hope this helped :)