I usually start picking up toiletries and anything we need to purchase before the trip about a 2 months out a little at a time when we food shop. That way we are not making a trip that will cost a bundle all at once before we go away. Then DH doesn’t notice how much I’ve spent either:) I also have a box in my closet with all our Disney essentials, park bag, badges, first aid bag, pins etc. Clothing, I start packing about two weeks.
I am a list person, so I have list after list going between clothing, toiletries and essentials.