How to save an item as bought in player prefs?

I have a Character Selection scene, in which you can see the characters once at a time and see the next or the previous one by ui buttons. Recently I've added money, and works perfectly, but I can't get to buy a character, and then save it in order to avoid having to buy it again. I have tried PlayerPrefsX, and i have an "Items bought" list but it all confuses me a bit. (Sorry for the long script)

 using UnityEngine;
 using System.Collections;
 using UnityEngine.UI;
 using System.Collections.Generic;
 using UnityEngine.SceneManagement;
 
 public class CharacterSelection : MonoBehaviour
 {
 
     private GameObject[] characterList;
     private int index;
 
     public List<GameObject> ItemsBought = new List<GameObject> ();
 
     public Button selectShipButton;
     public Button buyShipButton;
     public int cost;
 
     public Text moneyText;
 
 
 
     void Start ()
     {
         index = PlayerPrefs.GetInt ("CharacterSelected");
         characterList = new GameObject[transform.childCount];
         for (int i = 0; i < transform.childCount; i++) {
             characterList [i] = transform.GetChild (i).gameObject;
         }
 
         foreach (GameObject go in characterList) {
             go.SetActive (false);
         }
 
         if (characterList [index]) {
             characterList [index].SetActive (true);
         }
 
         ItemsBought.Add (characterList [0]);
         selectShipButton.interactable = false;
 
         moneyText.text = "" + MoneyScript.money.ToString();
 
     
     }
 
     void Update ()
     {
 
         if (ItemsBought.Contains (characterList [index])) {
             buyShipButton.interactable = false;
             selectShipButton.interactable = true;
 
         }
 
 
     }
 
     
     public void ToggleLeft ()
     {
 
         characterList [index].SetActive (false);
 
 
         index--;
         if (index < 0) {
             index = characterList.Length - 1;
         }
 
 
         characterList [index].SetActive (true);
         buyShipButton.interactable = true;
         selectShipButton.interactable = false;
 
     }
 
 
     public void ToggleRight ()
     {
         
         characterList [index].SetActive (false);
 
         index++;
         if (index > characterList.Length - 1) {
             index = 0;
         }
             
         characterList [index].SetActive (true);
         buyShipButton.interactable = true;
         selectShipButton.interactable = false;
 
 
 
     }
 
 
 
     public void SelectShip ()
     {
         PlayerPrefs.SetInt ("CharacterSelected", index);
         SceneManager.LoadScene ("MainLevel");
     }
 
 
     public void Buy ()
     {
         if (MoneyScript.money >= cost) {
             
             ItemsBought.Add (characterList [index]);
             MoneyScript.money -= cost;
             PlayerPrefs.SetInt ("Money", MoneyScript.money);
             moneyText.text = "" + MoneyScript.money.ToString();
             Debug.Log (MoneyScript.money);
 
 
         } else {
             Debug.Log ("Not enough money");
         }
     }
 }