How do I save a custom class of variables to playerprefs?

Eric, of course, hit the nail on the head. Below is a very simple serializer which you can use to save the file. This will not serialize all objects, because certain types (like Textures) aren't serializable using this method. However, for simple data it is quite effective. If you need to encrypt it, check out System.Security.Cryptography.

 using System;
 using System.IO;
 using UnityEngine;
 using System.Collections;
 using System.Collections.Generic;
 using System.Runtime.Serialization.Formatters.Binary;
 
 public class Serializer
 {
     public static T Load<T>(string filename) where T: class
     {
         if (File.Exists(filename))
         {
             try
             {
                 using (Stream stream = File.OpenRead(filename))
                 {
                     BinaryFormatter formatter = new BinaryFormatter();
                     return formatter.Deserialize(stream) as T;
                 }
             }
             catch (Exception e)
             {
                 Debug.Log(e.Message);
             }
         }
         return default(T);
     }
     
     public static void Save<T>(string filename, T data) where T: class
     {
         using (Stream stream = File.OpenWrite(filename))
         {    
             BinaryFormatter formatter = new BinaryFormatter();
             formatter.Serialize(stream, data);
         }
     }
 }

To use it:

 Serializer.Save<ExampleClass>(filenameWithExtension, exampleClass);
 ExampleClass exampleClass = Serializer.Load<ExampleClass>(filenameWithExtension));