How to create an eight point 3d character controller in unity with rigidbody enabled

hi dev, i'm trying to make to make an 8-point character controller in unity. for a 3d character so far this is all I've got.

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class NewBehaviourScript : MonoBehaviour
 {
     public Rigidbody theRB;
     public float moveSpeed;
     Vector3 moveDir;
 
     // Update is called once per frame
     void Update()
     {
         moveDir.x = Input.GetAxisRaw("Horizontal");
         moveDir.z = Input.GetAxisRaw("Vertical");
 
 
     }
 
     void FixedUpdate()
     {
 
         if(moveDir.x != 0  || moveDir.z != 0)
         {
             theRB.transform.Translate(0, 0, moveSpeed * Time.deltaTime);
         }
 
         if(moveDir.x != 0 && moveDir.z == 0)
         {
             theRB.transform.rotation = Quaternion.Euler(0, 90f * moveDir.x, 0);
         }
         else if (moveDir.x == 0 && moveDir.z != 0)
         {
             theRB.transform.rotation = Quaternion.Euler(0, 90f - (90f * moveDir.z), 0);
         }
         else if (moveDir.x != 0 && moveDir.z == 1)
         {
             theRB.transform.rotation = Quaternion.Euler(0, ((90f - (90f * moveDir.z)) + (45f * moveDir.x)), 0);
         }
         else if (moveDir.x != 0 && moveDir.z == -1)
         {
             theRB.transform.rotation = Quaternion.Euler(0, ((90f - (90f * moveDir.z)) + (45f * -moveDir.x)), 0);
         }
 
    }
 }