If your hair is dry and greasy at the same time, you definitely need some moisture! Since your hair is dry, your sebaceous glands are on double duty to get that hair moisturized with sebum... this is where the greasy feeling comes in. It's the same with the face - if your face is dry and oily, you need moisturizer to balance the oils. By using a conditioner, you are telling your glands, hey.. you don't need to produce so much oil, I've got this! It seems counter-intuitive, but that's how the body works.
As another poster mentioned, you can use as many or as little products as you want. Depending on the weather and what your hair needs. You may or may not need protein, but you can get that in your rinse out. Your rinse out can also act as your leave in. Or you could get one conditioner for everything. You can add your own kitchen oils to your base conditioner to use a deep treatment, so that's not really a necessity to purchase, unless you want to.
2c-3a - med width- low porosity - high density - growing out to donate
POOS: Sevi Seabuckthorn, Neutrogena Anti-Residue
RO/LI: Suave Coconut / KCKT
PT: CNPF, gelatine mix
COLOR: henna, amla & indigo
= humectants in low dews