By now you should have a room that is totally chametz-free where you can start to store your Passover groceries as you buy them. Matzah is something that needs to be bought as far in advance as possible, especially if you have a particular brand that you are partial to. The later you leave it the more of chance there will be that the store will be sold out.
When I shop for Passover, I try to get all the goods that I will need for the whole 8 days. I would rather not have to go back to the store to buy anything else if I don't have to. (One year I thought 144 eggs would be enough, and I ran out half way through the holiday, but that's a story for a different time).
Make a list of everything you'll need. In fact, I would take it a step further. Keep a list online, on a spreadsheet, of what you bought, and whether you used it, what you ran out of, what you bought too much of. This will give you a better guideline of what to buy and may keep spending a little lower. At the end of Passover, make a list of what you wish you had bought - and make sure you can find these lists for next year!
ACTION: Make a folder on your PC and title it "Passover". Save everything Passover related in it, and make a spreadsheet of your shopping lists.
DINNER TONIGHT: No-Bake Macaroni & Cheese - Not only is this ultra-creamy version of mac and cheese nearly as fast as the boxed variety, but your family will be able to pronounce every ingredient. If they aren't broccoli fans, substitute a frozen vegetable of your choice. On your dinner table in less than 30 minutes.