Just a quick response, but if you don't have them yet, great toys that will get years of use are:
toy kitchen with food and pots & pans
doll-sized high chair, packNplay/crib & stroller
kid-sized table & two chairs (if you have the room)
large magna-doodle
basic toys for play-doh - cutters, molds, etc, which can be supplemented with ordinary stuff around the house (or dollar store) and a supply of little tubs of different colors.
books, books and more books - especially collections like some of the hardcover collections of Little Golden Books, etc.
I always preferred 'imagination' toys over electronic stuff, and I stay far, far, FAR away from the Disney or other characters toys, especially if you want the toy to outlive the character-fixation (or be used by a sibling of the opposite sex.)
A trunk of dress-up clothes, or a travel case of fake 'jewelry' is also a good addition, as long as you'll have the patience to be helping her on and off with the bigger pieces of clothing.
Look for storage solutions at the same time. For example, I got my daughter 4 of these latching bins from Target. (Sorry, only link I could find with a pic is here: http://www.amazon.com/Sterilite-18960606-Showoffs-Storage... )
They stack, she can close them herself and they hold a fair amount of awkward-sized toys without getting too heavy for her to carry herself.
If you haven't already used that space, underbed bins are also wonderful - you can put smaller bins in them to keep toys grouped, or leave them loose - kids are already down on the floor to play, so these are easy access for them.