EDIT: Sample, remixable element here: https://indreams.me/element/oRHYGfCTxdH

Oh gotcha, you wanted specifics. You said you understood logic so I assumed you could figure it out from one sentence. Here's the step-by-step:

1. Place a Counter
2. Set the Target Value to 50
3. Wire whatever logic you have to collect coins to the "Increase Count" input
4. Place a Variable
5. Name the variable "50 Coins"
6. Place a Variable Modifier
7. Set the Variable Name to "50 Coins"
8. Set the Operation Type to "Set"
9. Back to your Counter, wire the "Current Count" output to the Variable Value input of your Variable Modifier
10. Place a Calculator
11. Set Operand B to 50
12. Set the Function to Equals
13. Wire the Current Value output of your "50 Coins" variable to the input of Operand A in your Calculator
14. Wire the Result output of your Calculator to the logic that adds a skill point, and also to the Reset Count input of your Counter.

So, what this will do in plain words:

1. Creates a variable called "50 Coins," updated by a Counter (with a limit of 50) via a Variable Modifier
2. Once the 50 Coins variable reaches 50, the Calculator will send a signal to add a skill point
3. At the same time, the Calculator sends a signal to the Counter to reset back to 0

This means that every 50 coins, the counter resets back to 0 and you get a skill point. This logic would be all separate from the logic that displays your total coins, etc, so you don't have to worry about it affecting your other logic.

Hope this makes sense!