Semi new to Lua, Anybody explain how you have a "printed" text go into a gui? (Purchase log)

Put this in your server script when the item is touched and purchased. You may want to fire a separate event of course for the actual purchase - I'd do a server function for that.

local AnnoucementEvent = Instance.new("RemoteEvent",game.ReplicatedStorage)
AnnoucementEvent.Name="GameToClientGuiEvent"
local istouched=false
	script.Parent.Touched:connect(function(part)
		
		if istouched==false then
			istouched=true
			if part.Parent:FindFirstChild("Humanoid") then
				print("firing the annoucement event")
				local player = game.Players:GetPlayerFromCharacter(part.Parent)
				local message = player.Name.." bought the item!!!!"
				
	       		AnnoucementEvent:FireAllClients(message)
			
			end
			wait(3)
			local message = ""
		
			AnnoucementEvent:FireAllClients(message)
			istouched=false
		end
	        

	end)
	

Then in a localscript under StarterPlayerScripts (I named mine PlayerAnnoucements)

local AnnoucementEvent = game.ReplicatedStorage:WaitForChild("GameToClientGuiEvent",10)
local Player = game.Players.LocalPlayer
local GUI = Player.PlayerGui
local AnnoucementScreenGui = Instance.new("ScreenGui")
AnnoucementScreenGui.Name = "AnnoucementScreenGui"
AnnoucementScreenGui.Parent = GUI
 

local AnnounementFrame = Instance.new("Frame")
AnnounementFrame.Name = "AnnounementFrame"
AnnounementFrame.Position = UDim2.new(1,-500,0,0)
AnnounementFrame.Size = UDim2.new(0,500,0,50)
AnnounementFrame.BackgroundTransparency = .5
AnnounementFrame.Parent = AnnoucementScreenGui


local AnnoucementText = Instance.new("TextLabel",AnnounementFrame)
AnnoucementText.Size = UDim2.new(1,0,1,0)
AnnoucementText.TextSize = 32
AnnoucementText.TextScaled = true
AnnoucementText.BackgroundTransparency = .5

AnnoucementText.Text = ""

function UpdateAnnouncementScreenGui(str)
	AnnoucementText.Text = str
end
AnnoucementEvent.OnClientEvent:connect(UpdateAnnouncementScreenGui)

There's plenty of room for improvement.. you may want to append the message....

I would have the AnnoucementFrame and Text elements already preset under StarterGui and so all the script has to do is set the Text value.. but I'll leave the rest to you to figure out... Let me know if you need more help.