How to Use Object Pooling for a 3D Autorunner? As Opposed to Instantiate?

So, for my project which is a Subway Surfers type game, I'm Instantiating when its clear I should be Pooling. My character moves along the Z Axis and I instantiate and then delete roughly 12 Obstacles every 5 seconds. My Draw Call is at a consistent 250 while my tris is at 144k.

How do I make a pooling system similar to my current system? Heres my current script. If possible, I want to make each tile seamlessly connect.

 using System.Collections;
 using UnityEngine;
 using System.Collections.Generic;
 
 public class TileManager : MonoBehaviour
 {
     public GameObject[] tilePrefabs;
 
     private Transform playerTransform;
     private float spawnZ = -10f;
     private float tileLength = 27.7016f;
     private float safeZone = 22.5f;
     private int amnTilesOnScreen = 4;
     private int lastPrefabIndex = 0;
 
     private List<GameObject> activeTiles;
 
     // Start is called before the first frame update
     private void Start() {
         activeTiles = new List<GameObject>();
         playerTransform = GameObject.FindGameObjectWithTag("Player").transform;
 
         for (int i = 0; i < amnTilesOnScreen; i++)
         {
             if (i < 2)
                 SpawnTile(0);
             else
                 SpawnTile();
         }
     }
 
     // Update is called once per frame
     private void Update() {
         if (playerTransform.position.z - safeZone > (spawnZ - amnTilesOnScreen * tileLength))
         {
             SpawnTile ();
             DeleteTile ();
         }
     }
 
     private void SpawnTile(int prefabIndex = -1)
         {
         GameObject go;
         if (prefabIndex == -1)
             go = Instantiate(tilePrefabs[RandomPrefabIndex()]) as GameObject;
         else
             go = Instantiate(tilePrefabs[prefabIndex]) as GameObject;
         go.transform.SetParent(transform);
         go.transform.position = Vector3.forward * spawnZ;
         spawnZ += tileLength;
         activeTiles.Add (go);
     }
 
     private void DeleteTile()
     {
         Destroy(activeTiles[0]);
         activeTiles.RemoveAt(0);
     }
 
     private int RandomPrefabIndex()
     {
         if (tilePrefabs.Length <= 1)
             return 0;
 
         int randomIndex = lastPrefabIndex;
         while (randomIndex == lastPrefabIndex)
         {
             randomIndex = Random.Range(0, tilePrefabs.Length);
         }
 
         lastPrefabIndex = randomIndex;
         return randomIndex;
     }
 
 }