what supplies are needed

Supplies for your knitting loom vary according to the item you are creating. However, you will need the basics, which include

Knitting loom
Knitting tool
Yarn needle
Yarn

Now, if you look at individual patterns you will see a variety of supplies you will need to create the different items such as: For round knitting looms for creating knits hats you will need:
Round knitting loom
Knitting tool
Yarn needle
1 skein of 4-ply yarn

For a quick looming a hat pattern you will need
Round knitting loom – size of your choice
Knitting loom tool
Yarn needle
2 skeins of 4 ply yarn

For creating a fuzzy, rolled brim hat you will need:
1 child knitting loom
1 knitting loom tool
1 skein of thick, soft, chunky yarn

For knitting a Christmas stocking on a round knitting loom you will need:
Baby/Toddler hat size round knitting loom
Knitting Loom Tool
1 Skein holiday yarn
yarn needle

As you can see, the supplies are pretty much the same. You will need to know what size loom you need and how much yarn in order to create the pattern.