I want to make a “messaging system” in a gui. Basically I want the player to pay an amount in coins to send a message to another player. In one gui the player would send the message after paying, and in another the player would receive the message, like an inbox.
Every help is welcome 
You may use Remote events to do this.Client-Side will send the message and target Player to the Server-Side and Server-Side will update the target player’s gui.Hope this helps!
I forgot to say about paying system.If you want to make the system.I recommended Checking on Server-Side.Client-Side is dangerous.