A simple spell that I've done for success is just to carve a related thing into a golden or orange candle (it can be a sigil, a symbol you associate with success, or just the word "success" or "luck" ) and then burn the candle while imagining doing well. You can chant something if you wish (again, this can just be saying "luck" over and over if that feels right).
I've made a tea with ginger, allspice, and a drop of lemon juice before theatre auditions for soothing nerves and giving me confidence, and I found it to work well for me. You could take out/swap ingredients as needed. While you stir in honey/sugar, visualize tranquility and confidence.
A ritual I've done that I found incredibly helpful for confidence is to run a bath and put cleansing ingredients in (it can just be salt, if you want, but herbs are great too). Write down the things you want to wash away (such as stress, doubt, etc) on a piece of paper with a pen that will run. Take a bath. After you get out, put the paper in the water and watch the words wash away. I chose to air dry, but if your bathroom is freezing you can towel dry. After that, write the qualities you want to manifest (confidence, success) on a piece of paper. You can decorate this one up if you choose.
I've done a type of meditation where I just hold a smooth rock and pour my anxieties into it. Then I put it outside for a few days to "reset."
I've found stimulants to add an extra spark to spells, especially to give your energy a little fiery confidence. Things like coffee can really add some zest. This could even be something just like visualizing success while having a morning cup of coffee. If you can't drink coffee for whatever reason, burning coffee beans (safely!) can add this spark, as well.
I've seen people enchant their makeup for confidence, which could definitely work in this situation. You could put sigils or other symbols for luck and confidence on your makeup containers.
I hope that helps, and good luck! I'm sure you'll do wonderfully. :)
