Shampoo? For starting dreadlocks?
Good dreadies with clean scalp and happy dreads wash every 2-3 days max. So that's 2-3 times a week.
1 cup of water with 2 tablespoons of baking soda in a squeezie bottle(like the kind you'd find in a box of hair dye) is PERFECT for hair your length. No need to make more than that. Shoot it in your roots and then the rest of the length of your hair, let it sit for five minutes, rub your scalp with your fingers(if you want), and then rinse. Easy peasy lemon squeezy.
For the ACV, some people do it while others don't. It DOES balance the ph of your scalp but it can also be too moisturizing for some people. Trial and error. I quit doing it after four months because it made my scalp feel kinda oily. But it's a trade off. I had to deal with drier hair. You have to do what feels best for you.
Generally speaking, it's 1 cup of water + 1/2 - 1 whole teaspoon of ACV. Do this after the baking soda is completely rinsed out of your hair. You just have to let the ACV rinse sit on your head for about thirty seconds before rinsing.
I advise adding any essential oils you want to your baking soda. Others say you should put it in your ACV and others say that a spray bottle works best.
Whatever you choose, use caution. You can use 3 drops of basil and feel a good cleansing tingle but use up to 10 drops of lavender and feel like you're in a spa. If you tried to do the same thing with basil you'd be screaming with a burned scalp. See? Every essential oil has their own attributes. Use caution. But have fun experimenting. I never would have thought to use basil in my hair but I had some in the closet and was running low on my lavender and hey! I learned of a new way to easy itchies! Basil is great for it. Interesting how that works out.
Have fun with it. Trial and error is how we all learn but you've come to a great resource, Back2Dreading.