Spawning Coins infront of the player

Instantiate is a heavy operation: it allocates and initializes lots of memory blocks for each object created. When the object is destroyed, these blocks become useless, and at certain times another heavy operation called "garbage collection" must be executed by the system to make this memory available again.
In order to reduce these performance killer operations, you can create an "object pool" for the coins: it's a list that keeps the coin objects; instead of destroying a coin, deactivate it; instead of creating a new coin, re-activate one of the deactivated coins at the desired position/rotation.
An object pool can be easily implemented using List, like below:

 import System.Collections.Generic;
 
 var coinPrefab: GameObject;
 var coinPool = new List.<GameObject>();
 
 function IsCoinFree(coin: GameObject): boolean {
   return !coin.activeInHierarchy;
 }

 // use this instead of Instantiate:
 function InstantiateCoin(position: Vector3, rotation: Quaternion): GameObject {
   var coin: GameObject = coinPool.Find(IsCoinFree); // is any free coin in the pool?
   if (coin){ // yes, this coin is free:
     coin.SetActive(true); // activate it...
     coin.transform.position = position; // at the desired position...
     coin.transform.rotation = rotation; // and orientation
   } else { // no, all coins are in use:
     // instantiate a new coin:
     coin = Instantiate(coinPrefab, position, rotation);
     coinPool.Add(coin); // and add it to the pool
   }
   return coin; // anyway, return the coin GameObject reference
 }

 // always use this to destroy the coin:
 function DestroyCoin(coin: GameObject){
   // just deactivate it - the coin now is free in the pool
   coin.SetActive(false);
 }

The idea is simple: when you want to create a new coin, call InstantiateCoin(position, rotation): this will first search in the pool for free coins; if there's a free coin (deactivated) in the pool, activate it at the desired position/rotation and return a GameObject reference to it; if there's none, create a new one as usual, add it to the pool and return its reference. When you don't need the coin anymore, "destroy" it using DestroyCoin(coin): the coin is simply deactivated, so that it disappears from the scene and become available in the pool (deactivated objects in the pool are considered available).
NOTE: If the coins have their own scripts, you may have to call a custom Start function to initialize their variables, so that a recycled coin behaves exactly like a brand new one.