Well somethings you must take and others are up to you, I will give a list of things that you must take with you on every fishing trip and most will properly be a rule at the place your fishing
A good decent size landing net is a must along with a padded landing mat.
Carp care ointment, it may sound silly but the only med check a fish will normally get is when it's caught, cuts and grazes ain't uncommon on carp so if you see one apply the correct ointment to either it's mouth or body.
Alcohol rub, wells disease is talked about all over the net so before you go biting in to the sarnies you made prior give you hands a clean OK.
These 4 things are a must for me OK!
After the 4 main ones it's all down to you and how you want to your fishing trip to be so things like
A bivvy,waterproofs,radio, refreshments,sunglasses, cooker and snacks all help but not essential.