Is there a spell on becoming a good witch?

A witch is just someone who casts spells, so if you cast a spell, you are already a witch.

Are you talking about a dedication spell? Here is a simple one:

You need:

A white candle

a clean space on the ground outside

A lighter or match

(you can add pomegranate juice, a cup or chalice, and homemade bread on a plate)

Go outside at night and draw a circle in the dirt big enough for you to sit in comfortably. Put all your stuff inside the circle in the middle. Meditate on what it means to be a witch, and what it means to you to dedicate yourself.

When you are done, walk around the circle, stopping at each elemental direction (East, South, West, North) and send a little prayer towards them. You arent going to invoke them tonight, you are just asking for Their attention for a little bit. When you are done, sit in the middle of the circle and send another prayer to the God and Goddess and ask for their attention as well. Light the candle. Then say aloud "Tonight I ask for Thy attention, for tonight is the night I dedicate myself to you." Then tell Them what you want.

When you are done, (if you brought the bread and juice) hold the cup up into the sky and say "Blessed be this juice" and take a sip. Do the same for the bread, and say "Blessed be this bread" and eat it. Dont eat or drink it all just yet.

Say aloud you are now dedicated and thank everyone again. Their attentions should shift away from you. Now you meditate on what you will do from then on to walk the path of a witch. Really think about the commitment you will have to make. When you are done, drink and eat most of the food, and then pour out the juice and bury some of the bread as an offering and a blessing. Clap thrice, then erase the circle. Ground, eat if you are still hungry and then go sleep.