A common mistake people make when first tackling their clutter problem is that they go out and buy a bunch of storage containers to start organizing. Containers and boxes and baskets and organizing gizmos and so on. The problem with this is that it doesn’t solve your problem. You’re not getting rid of the clutter, you’re just organizing it, hiding it, and making it look slightly better than it did before. However! This is not permanent. If you get rid of something, it’s gone from your house for good. If you organize it, you’ve now just made the decision to add it to the list of something to maintain, because you KNOW it’s not going to stay in that spot.
Now, I’m not saying organizing is bad, it certainly isn’t! But decluttering before you organize is very important. If you do it the other way around, you don’t know how many or what kind of storage containers you’re going to need. Try to get rid of as much as you can before you organize what’s left.