If you want to take care of your hair naturally and don't know where to start, I highly recommend the vegetable oil bath for hair; ultra simple and inexpensive technique.
This suits all hair types; what will change is the oil used and the frequency of care. If you have cold-pressed organic oil in your kitchen (olive oil for example) you can even start right away.
This will nourish your hair intensely and there is a good chance that you will be amazed at the result, especially if you have dry and dull hair. It's important to understand that to have beautiful hair, the oil bath is good but it's not enough! This must be part of a global approach to getting back to nature.
Here are pictures before and after. The brightness was not the same at all, but you can still see the difference.
(Before) 
(After) 
Here's how to do it:
Step 1: Untangle your hair as usual
Step 2 (optional): Moisten your hair with your hands under water or with a spray if you have one. This step is optional as it can be very embarrassing to have wet hair for several hours, especially when you leave the oil bath on at night.
Step 3: Take a very small amount of oil (or vegetable butter) and start coating your hair strand to strand. Do the same all over the hair.
Step 4 (optional): Coat your fingertips with oil and gently massage your scalp. This step is optional because depending on your hair type, you may only need this treatment at the ends and lengths.
Step 5: Wrap your hair in a towel and leave for a particular time (at least half an hour; but leave it for as long as possible; overnight if you can).
Step 6: Wash your hair with your usual shampoo. It is often necessary to make 2 shampoos toget rid of the oil bath entirely. You can then do your usual treatments, it doesn't change anything.
This is by far my favourite treatment of all time because it brings a real nutrition to the hair. It is important to know one thing: this care brings fat to the hair, so good. However, it does not hydrate. It must therefore alternate with other treatments for an optimal result. I will soon write an article about the difference between hydration and nutrition and give you some tips to understand the needs of your hair.
To conclude, you only need two things; a good cold-pressed oil, and time in front of you. If you want to try the experiment, don't hesitate to give me your impressions in comments.