One of those "how long is a piece of string" questions and you really need to think about needs. As in;
Keeping warm, cool, wet or dry. Well fed and no biting things. How do I keep comfortable, washed and content. How do I extend this to others in my party? Have I planned well enough and is the first aid kit well stocked?
My experiences started one morning at 2.00am when I opened the door of the car and called to Dad "I'm trying to sleep but I can't keep warm!" whereupon he came over with an extra blanket for me. There was frost on the car and the ground. I was 11 and it was 1959.
My best advise? Buy "the bit" that fits into the vehicle where you want it to fit. The "bit" should be the best you can buy for your budget in that financial year. (think about it) If the "bit" is something to do with sleeping, never, never skimp. Look for bargains but never buy budget. Golden rule this one.
If the "bit" needs to keep food fresh, again don't skimp. Or at least for the first year.
Full tummies are tummies that will come camping again with you.
You will change your tent. None seem to fully fit the bill in my experience. I hear this from others as well.
Cooking gear is an evolving thing and it really comes down to what and how you cook at home. Don't venture too far away from your proven techniques as this will invite disaster. Always, ALWAYS trial run a new dish cooked in the camp oven (or Cobb, or whatever) AT HOME, then do it in camp. This sorts out the gear as well. Helps with planning out a menu for the week. Do plan as it help with the shopping and stocking the coolbox (see above).
Do a list with the family/co-campers and work off the list. You WILL forget things.
Don't forget the camera and tripod......