N.B.
Imaginative play...access to books....things they can attempt to count and sort...build and create with. Much of this is stuff you can make too.
I do home childcare (all my 7 daycare kids are 3 and under in age) and some of the most used and loved toys are things I have made. Old formula cans filled with things. File folder games I have laminated..sequencing cards too (like a 3 or 4 part thing, such as baking cookies or getting dressed).
We save milk and juice type jug tops...a few of my daycare parents remember to save them for me as well. We have quite a few now. They are great for doing counting things, for pattens and sorting (early math)..for putting a few into those old formula (or peanut cans..I have a few from some cookie recipes I just made)...they clank and make noises for instruments.
Make a flannel board (get rolled felt from the fabric store and any old piece of thin wood....one of mine was recycled from the backing of an old bookshelf that we just made an open shelf instead)..then just stretch the felt over and staple gun it to the wood. Really really heavy duty cardboard works too if you have access. You can make one large one for the wall or make a few lap size small ones. Then make felt pieces for them to act out stories (or you to tell some simple stories)..or just random pieces for them to make things up..sort of like paper dolls in a way. You can also buy them on line. I make many of my simple shaped ones from the large puzzle pieces I have..trace and cut out with sharp scissors.
Also another thing I am making soon...a friend has one....a tent made to fit over a regular old folding table. The square for the top piece, and the side portions...then one side, you put a zipper in it, so You can zip it up..or just finish the cut edges and make tie backs (then no one is getting trapped inside with it zipped up..just flaps like a teepee then).
Have a large variety of things like Little people toys (I buy the small pieces at garage sales and thrift stores, clean them well with bleach water, etc...but mine are all one size...the one older size, non choking, that they made for many many years before they started messing with the sizre and dhape of them)...plus Duplo Lego's. Those 2 things, along with my tiny, very plain wooden toy kitchen and alot of sturdy toy food...and cheap dollar spot (target) baskets...Oh My they love baskets with handles..we have about 20 in my playroom )..these are the most overall played with things in my full playroom. The More simple things...which I prefer. Then they really use their imagination.
We also have some great simple dress up career outfits I got thru Discount School Supply..the toddler set. ( http://www.discountschoolsupply.com/Product/ProductDetail...) They are fabric and wash up great. They love to just wear the smocks cuz they have pockets on them and they can put their "stuff" in them. Alot of pretending and making stuff up going on. We don't watch much TV..and I almost never do worksheet type stuff...occasionally for matching activities, but thats just not my thing. We do hands on activities, we bake and we use our imaginations. Its what works for us!
Good luck....