I've seen in some games a GUI that will randomly pop up that promotes a gamepass and you can click the GUI and buy it and I've seen them do that telling people to follow them on twitter or promoting another one of their games. I would like to do this for gamepasses can anyone help me because I have no clue where to start!
Well, it's mainly knowledge of how to create a GUI. Once you know how to design it to your preferences, you'll need some property toggling knowledge. Setting the value to true and false. In most games, the GUI only pops up when they first join the game, and from that point on, they have to press a TextButton or ImageButton to make it come up again. The way they have it come up when you first join the game, but not when you spawn is by using the PlayerAdded Event and cloning the GUI into their PlayerGui. In GUI's they may have their own Purchase button, and say the price, but then it'd soon prompt another GUI that is created by the Marketplace Service. They use the PromptProductPurchase Method to have the ROBLOX made GUI come up.