Ha! I could have written your post - right down to the 900 sqft! You didn't mention your dd's age or what kind of storage you already have, so I'll just tell you how we've accomodated the kid stuff up to now. Our dd is almost 4 1/2 and the toys started becoming a major problem around her 3rd birthday.
1 - The living room is toy free. This is strictly for my own sanity. She can play in there, but the toys must be GONE by dinnertime.
2 - We have an island in the kitchen. One shelf is for kitchen-type toys - play food, play appliances, cash register. Also used for art supplies until recently. Art stuff is now in a 3-drawer rolling cart that slides under our easel.
3 - We have a tiny useless space off the kitchen. It's basically an extra wide hallway. That is our "play pit". Dh built a large shelving unit that can accomodate anything 16" deep x 16" tall, with lots of smaller shelves too. I actually bought the storage containers FIRST - some fabric cubes, some plastic totes. I bought a couple extra, anticipating toys she wasn't yet playing with, but would be soon (like Barbies and legos). We then built the shelf to accomodate every toy we could imagine wanting to put there!
4 - Once the shelf was built and full, we established a rule: Anything new will REPLACE something old. We made sure all the relatives knew this too. My MIL is notorious for filling our house with garage sale "finds". We did our best to explain that anything new will require dd to throw something away.
5 - My dd's bedroom is a study in storage solutions! There is no closet, so we stacked a 5-ft "laundry" cabinet on top of her small dresser, making our own armoire. 4 shallow drawers, 3 feet (wide) of hanging space, room for shoes in the bottom of the hanging space, and 2 large shelves above for the next 2 season's worth of clothes (too-small clothes go to a bin in my closet to be passed on twice a year).
6 - Dd's bed has drawers built in underneath that are perfect for dress-up clothes (just cram 'em in). We also got the matching headboard for: jewelry box, GIGANTIC Disney princess musical snowglobe (MIL), books, tissues, misc. "special" stuff (like rocks, pompoms, ribbons, boxes, anything she just LOVES at the moment).
7 - We got a 6-ft bookcase for her room - lower sheves house books, coloring stuff, beading supplies, craft supplies (all in bins). Upper shelves hold special toys like her piggy bank and special plush toys, plus extra bedding supplies.
8 - The toy "box" in her bedroom is the style that has 3 bins below, and the top lifts to show a shallow storage space. We use the bins for doll clothes and one "junk" bin. We don't use the upper storage, because there's a dollhouse on top. But someday, that space may be good for school supplies, and I could make a cushion for a seated reading area.
9 - Stuffed animals live in one of those net things. She rarely plays with them anyway. I threw out half a year ago, and she never noticed.
10 - We have a hanging mesh shelf thing and a couple wall-mounted shelves too - just to get more stuff off the floor.
11 - If I could have afforded it, I would have bought a child table with built-in storage. The plain table works fine, but I just see it as wasted storage space!
And finally, we are fairly strict about cleaning up. We use a reward system to help her, and we remind her to start tidying while we make dinner each night. Our house is still cluttered, but I think that's just a family thing. I suppose I'll miss it someday.
Good luck!