Is it just the clothes that are messing the apartment up, or what is it that is the problem?
I totally agree with USAmma, get rid of toys! My kids used to have so many toys, that they'd take them out, spread them around the house, and that was it. They never really played with them, just took them out and dumped them all over. I took some time to get rid of most of them. The junky ones went out immediately, or the ones I knew they wouldn't miss. The ones that I question I would put in a box down the basement, and if after a certain time they didn't ask for them, I got rid of them. Now they have a lot less toys, but play with what they have. I also did the same with movies. The ones that were liked but never really watched were taken to donate to the library to "share" so the kids know they can still go and rent them when they want them, and all we have are a select few of the really loved ones. We don't buy them anymore either.
Get rid of as much stuff as possible that you don't use. It might have to be a gradual process, as in my case, but it's working great. There has only been one thing that I wish I wouldn't have gotten rid of, and I can't even remember what it was!!
To organize, add shelving where ever possible. I added two shelves to my pantry, and dh built a unit in the basement. Collect Rubbermaid-type bins, shoeboxes, reg. boxes, and a marker and pack things away. Stick them in closets, under beds, anywhere that you have space. HTH