Correct way to spawn and move objects

So im creating a game where a player or multiple players will create different type of spells and throw at eachother.

Now since im rather new to unity im very uncertain if i am doing it the wrong way and i want to make sure that i dont get any bad habits.

So i have a player GameObject with the following script attached

 public class PlayerCasting : MonoBehaviour {
 
     public GameObject Spell;
 
 
     // Use this for initialization
     void Start () {
     
     }
     
     // Update is called once per frame
     void Update () {
         if (Input.GetKeyDown (KeyCode.C)) {
             GameObject newSpell = (GameObject)Instantiate (Spell, transform.position, transform.rotation);
         }
     }
 }

Now the spell prefab has the following script

 public class BallScript : MonoBehaviour {
     public float speed;
     // Use this for initialization
     void Start () {
     
     }
     
     // Update is called once per frame
     void Update () {
         transform.Translate (Vector3.forward * Time.deltaTime * speed);
     }
 
     void OnCollisionEnter(Collision col){
         Destroy (this.gameObject);
     }
 }

Now my questions are.

1. My idea is that each spell in my game will be created in the following way with a prefab. Later on i will be adding effects and removing the actual ball. So question 1 is, is it correct to create such a game object each time?

2. Hopefully this game will turn into a multiplayer game can i with the script above inflect dmg and manipulate other game objects properties such as health with the ballScript?

3. Lastly am i following the best pratice rules of creating items in a world or will i run into performance issues?

I hope you guys can give me some guidance as i really want to master this!