character select (code attacted) how to make lock /unlock system?

Hi friends, I have a simple character select screen left right to select character models. I have attached the code.

Can someone please advise on how i can get ie 1st character free, 2nd character 100 coins`3rd character 100 coins etc.

Thanks very much for any assistance

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.SceneManagement;
 
 public class CharacterSelection : MonoBehaviour 
 {
     private GameObject[] characterList;
     private int index;
 
     private void Start()
     {
         index = PlayerPrefs.GetInt ("characterSelected");
         characterList = new GameObject[transform.childCount];
 
 
         //fill the array with our models
         for(int i = 0; i < transform.childCount; i++)
         characterList [i] = transform.GetChild (i).gameObject;
 
 
         //We toggle the renderer to hide objects
         foreach (GameObject go in characterList)
             go.SetActive (false);
 
         //we toggle the sellected character
         if (characterList [index])
             characterList [index].SetActive (true);
 }
     public void ToggleLeft()
     {
         //toggle off the current model
         characterList [index].SetActive (false);
 
         index--; //index -= 1; index = - 1;
         if (index < 0)
             index = characterList.Length - 1;
 
         //toggle on the new model
         characterList [index].SetActive (true);
     }
 
         public void ToggleRight()
         {
             //toggle off the current model
             characterList[index].SetActive(false);
 
             index++; //index -= 1; index = - 1;
         if (index == characterList.Length)
                 index = 0;
 
             //toggle on the new model
             characterList[index].SetActive(true);
 }
     public void ConfirmBtn()
     {
         PlayerPrefs.SetInt("characterSelected", index);
         SceneManager.LoadScene ("Game");
     }
 }