I swap and change all the time because when I was a teenager that was the standard advice in J17 - so your hair didn't get "used" to a product
. My upper limit is about £20 a bottle, but I'll also use £1 stuff too.
For reference, I have coloured hair (an expensive balayage) which is prone to both grease and frizz so I usually try and get products which are fairly kind to my hair and if they're expensive j see it as protecting the money I've already spent on my colour. I wash my hair every other day or occasionally it's 3 days between washes. Anyway, my verdicts:
Tigi Bed Head - brilliant, but price can be variable so I wait until they're on offer. Good VFM though as huge sizes.
Lush solid bars - love the shampoo, especially the one that is good for psoriasis. I like the way my hair feels after using the conditioner but always find it a bit awkward to actually use. Hair feels super clean after using both.
Bleach toning shampoo and conditioner - about £6 each but can usually get on offer. I use the smokey blonde and it's perfect for livening up my colour in between hairdresser visits. Tend to use once a month, plus the Garnier Ultimate Blends mask (about £4).
Supermarket ones - Treseme, Herbal Essences, Alberto Balsam etc - much of a muchness. Fine as they go, but can tell my hair's not as smooth but not really a problem if I use a decent styling product too.
Bumble and Bumble - I like them, but not more than the Tigi ones I don't think.
Umberto Gianni - forgot about these! I used to leave them so thanks to the poster above who mentioned! Will look out for them in Home Bargains.
Aussie shampoo and conditioner - great, and decent value. I think these actually strengthen my hair too.
I do tend to spend on serum-type products. Bumble and Bumble's oil is good. I like Beauty Protector's Detangling Spray (think can only get via birchbox), Frizz ease and there's a solid coconut wax type thing in a tin from the Bodyshop that lasts FOREVER. You only need the tiniest amount to tame stray hairs.