You can put a text object on your layout. After you create a instance variable on the text named "Score". You've guessed that it will be a number a 0. You go to your event sheet. It will be something similar to this :
Every tick : Set text to text.Scorevalue
After, you will add your player on collision with gold (for example)
Player on collision with gold : Add 1 to Score
Every tick is a bad idea. Just make a function "Score.Add"
On Func "Score.Add"
-> System -> Add to Score [Function.Param(0)] //which is the passed score
-> Textobject -> Set text to [Score]
This keeps the performance of your game high. Then the text obj. will only be updated when the value has changed, and not every tick.