Help! Shampoo/Hair treatment for highlighted, fine, dry blonde hair that's breaking at the ends?

[Itstheimplication]

I'm lost - there are so many products!
My hair is highlighted and heat damaged. It's very very thin after pregnancy as well, and keeps breaking off at the ends. I'm going to get it trimmed but can't afford to lose too much off the length and wondered if anyone could recommend a good shampoo and conditioner and hair treatment to get rid of the dryness at least?

Castor oil, buy it is a bottle from a £1 shop or cheap greengrocery store. Leave it on overnight or for about 20 mins then shampoo as usual.
Alternatively, do the same with coconut oil - it's less sticky than the castor oil.
I use Shwarzkopf strengthening shampoo from £1 shop, and Avalon Organics peppermint strengthening conditioner, which i really like.

Sounds like my hair so I'm watching !

Would washing it with conditioner instead of shampoo help? I do that sometimes. It seems to be the same as if I used an expensive moisturising shampoo.

Thanks for the tips. When I wash with just conditioner it ends up somehow being greasy at the root and dry at the ends!