New to tile map creation, question about position of tiles

I am trying to create a basic tile map script to learn Unity and I am unable to understand why my tiles are spaced so apart and I can't seem to control their spacing.

My understanding of tile maps are limited but here is what I want to do. I want to be able to set tile size, amount of tiles displayed and the spacing between each tiles.

Image: http://puu.sh/in6XW/416f8971bc.png

 public class TileMap : MonoBehaviour {
     public Transform tilePrefab;
     public static int TILE_WIDTH = 32;
     public static int TILE_HEIGHT = 32;
     
     public float tileSize = 0.1f;
     private Transform[,] tiles;
     // Use this for initialization
     void Start () {
         var w = 18;
         var h = 15;
         tilePrefab.gameObject.GetComponent<SpriteRenderer>();
         tiles = new Transform[w,h];
         
         for (int y = 0; y < h; y++)
         { 
             for (int x = 0; x < w; x++)
             {
                 Transform tile = Instantiate(tilePrefab, new Vector3(x* tileSize,y * tileSize,0),Quaternion.identity)as Transform;
                 tile.parent = transform;
                 tiles[x,y] = tile;
             }
         }