i picked up some argan oil from primark for £2. i use this 1-2 times a week and thoroughly rinse after - and loads of people comment on how shiny my hair is. i've recently had 8 inches of hair lopped off in favour of a layered messy bob. i love literally washing and going to work! many of the reviews for this product state it is quite heavy on fine hair and can leave it a little lank and heavy as it has silicone in it:
http://www.amazon.co....ct-reviews/B0083H8ASG
I've tried the argan and the elvive. The elvive stuff is definitely a lot lighter - I've got fine hair too and I find the argan stuff makes it feel quite lank.
If you can get it I would advise L'oreal Professional Mythic Oil Milk, it must be the milk and not the actual oil though. It is brilliant stuff and not even slightly oily or heavy.
I've been using it for about a month-and i love it. I've got quite fine wavey hair,and I need a lot of mousse to give it body. The Extraordinary oil keeps it looking shiney and bouncey and seems to remove any build up of product.
I'd say the bottle would last about 6 months-if you use 2 drops a day.