So what to get ? Where to Begin??
The question isn't usually what toys to acquire, but what toys to get rid of. Most mainstream programs for children have way too many toys. Bins and Bins of brightly colored plastic toys. Besides being messy and disorganized, it sets the kids up for a life-time of materialism. I'd get rid of anything sharp, broken, or ugly. I'd also get rid of things that don't foster creative play.
Books:For a home with younger children (4 and younger) I wouldn't get a lot of books because their eyes aren't mature enough to scan them. If you love books, you could have a few of your more beautiful ones around for them to look at the pictures, or maybe a few board books, but toddlers don't take good care of books, so I'd get rid of them in general, or put them away until later. Once they hit 4 years old books are wonderful way to build upon their imaginations and inspire their creativity.
Plastics and other synthetics: These don't promote the healthiest development in children. It's hard, but purge the plastics. (There are, of course, exceptions - for instance I like plastic slides (outdoors) better than metal ones for safety reasons. I also prefer plastic shovels for outside because they are durable.) I think limited plastics or getting rid of them all together is the way to go!
Take your clues from the places where children thrive.
The Beach: Children don't need toys at the beach. Just water, sand and maybe a shovel and pail - maybe a ball as well. To bring these elements to children, be sure your space has access to water (a large bowl or tub full of water outside is fun) and earth (a sand box or better yet, a hill of sand - or just the dirt in the yard). Water and dirt are difficult in pre-school/day care settings because usually there are too few adults to help clean-up and change clothes, but in parent/child classes you can get away with it. Sand is nice because it's relatively clean. Have plenty of shovels and pails and stainless steel bowls and such to play with in the water and sand. Kids this age can't be asked to share constantly, so have lots of the same thing. (Lots of the same shovel, for instance.) Access to the outdoors and this sort of play are essential. Even in cold weather, large amounts of time can be spent outside if the children are dressed well. Yes, and I'd get some balls.
The Woods: No toys needed here either. Kids love to build forts and play imaginative scenarios in the woods. To bring these elements to the children, I like to see homes and places with all sorts of odd pieces of wood outside to play on. Maybe some logs or stumps. Maybe some planks (well sanded ones are best). Maybe some tree limbs. Things you can help them move around to create castles, or barns, or houses or stores or an endless amount of things.
The Home: Just regular things around the house are used by children for play. Do you remember making huts out of all the couch cushions as a child? Or draping sheets over the table to make a house? To bring these elements to children, I love to see furniture that can be used by the children when they play. Chairs turned on their sides. Tables that aren't too heavy to move around. Large silk and cotton cloths have endless uses for creative indoor play.
Round it out with items from nature, such as pine cones, stones, feathers, seed pods. Children find endless ways to play with these.
Think Tools rather than Toys: Some of my favorite "tools" for children are: child sized mops (the kids love these - I like the ones with wooden handles and cotton yarns, rolling pins (lots of the same one so children aren't asked to wait or share), child-sized baking dishes (real ones) such as pie tins, bread pans, little whisks (I happen to like these, but they aren't necessary), a washing board.
Just Toys: I happen to like well-made, wooden dump trucks (but I don't let them go outside). Also things you've made, or someone else had made for the children - dolls, doll clothes, ropes (from finger knitting), knitted animals, felt balls, etc.
I Really Enjoy Montessori and Such to get items or we just shop at thrift stores or make our own ;)