Is it worth to buy lens kit for mobile phone, ?

Namaste ! everyone
well first of all i tell you all am not a professional photographer ,or want to be.
i just loving to capture light in my phone. i want to do some little experiment. now i think to purchase lens kit for my mobile phone camera. but am bit confused to buy this thing. i have some little query regarding mobile lens kit.

1. how much i have to spend to buy a good quality lens ?
2. i have 2 phone (iphone 5s/galaxy s4) . is there any lens kit which compatible to both of my phone ?
3. which company/brand have best lens ?
4. & it woth to buy a lens kit ??