I love a good de-clutter. Stick on some feel good music and tackle one room at a time.
Get a bin pile for anything broken, charity shop pile (and I always have a separate pile of things I think friends kids can make use of) and sell pile.
One simple rule in our house, if you don’t use it loose it.
It’s OK to have 10 of something if you use them but can’t have 1 of something that hasn’t been used ever or in a year*
*exception for seasonal items/toys/clothes
After the initial de-clutter I keep one callax box in my airing cupboard where we put things as and when the kids decide they don’t want/need/have outgrown it and once the box is full we wort through sell/donate/pass on
I have come across a fb group called Organised Mum Method and helps people keep on top of it all