I'm sorry but, I don't get these substitutes for stuff. Please give an example for a gun costing 20$ and is going to the "zombie slayer"
Ok. You kill a zombie. Events should be:
OnZombieDeath > Client > VCE_ModVariable > Points [ADD] 5
The player now has 5 Points. Now you need a brick that you'd click to purchase the gun. Say it was selling Gun for 20 Points.
The event would be like this:
OnActivate > Client > VCE_IfVariable > Points [ >= ] 20
OnVariableTrue > Player > AddItem > Gun
OnVariableTrue > Client > VCE_ModVariable > Points [SUBTRACT] 20
OnVariableTrue > Client > CenterPrint > [<color:ffff00>Total Points Left <color:ffffff>- <var:cl:Points>
OnVariableFalse > Client > CenterPrint > [INVALID AMOUNT OF POINTS - <var:cl:Points>/20]
If you have 20 points, It'd subtract the points and add the gun to your inventory. You need to download the Add Item event. Its very easy to find if you have RTB. The <var:cl:Points> will display the points you have. And if you have a problem with this, You either messed up on setting the Client or Player events.