Button to activate lua function

Hi I’m new to gmod, and I learned a bit about lua scripting from gmod wiki. I need a way that when the player presses a button, a function happens, with a different function for different buttons. I have an idea for a great game, and this is the last thing I need.

I mean a button like one placed by the button tool, or something similar to that. What I’m making is a system where when the player presses a specific button, they lose a certain amount of money, which is saved to a variable, then get ammo for a specific weapon. Different buttons throughout the map give different wepons and ammo. I already have the code to pay for and spawn the weapon, I just need a button to activate it.

Also, is there any way to set where the player(s) spawn(s) when the map first loads, and after that?

This should get you started: http://wiki.garrysmod.com/?title=Gamemode.PlayerUse

Are you talking about a Derma Button. If so try this
DButton.DoClick = function()
Replace DButton with the name of your button.