Personally I follow this guys hair routine (shampoo, conditioner, leave-in conditioner, hair oil) and my hair looks fantastic. I don't buy the exact products he recommends (well half of them) because they are very expensive but I have seen great results since I started taking care of my hair better. His shampooing and drying technique advice was also useful (I was guilty of shampooing wrong and "machine wash" drying my hair with a towel).
I don't use his own brand shampoo and conditioner because it's $75 USD for 236ML / 8 FL OZ for a set. His shampoo conditioner set would cost $318 USD for 1 LITRE or $159 separately, while I pay $157.42 USD for BOTH my shampoo and conditioner (1 LITRE) that's half the price. Yeah that's still pricey but it's "professional" shampoo and I have seen a difference in my hair and frankly it lasts me many months so it's worth it for me. Could I find a cheaper "drug store" brand shampoo/conditioner that works? Sure but I don't want to spend time and money testing different products at the expensive of my hair health.
As for the leave-in conditioner and hair oil he recommends, I have both. I bought them both in August last year for $22 USD (leave-in) and $26 USD (hair oil) respectively (I got a small discount).
So far I've used about 1/5 of the hair oil and 3/4 of the leave-in, so I those two products have definitely been worth it for me.