Starting a play group with your preschool child is a great way to help your child socialize and learn building blocks for later learning. When I purchased my Montessori equipment at Nienhuis years ago there was a huge display area of developmental toys for toddlers and young preschool children. It included blocks, bricks, cars, puzzles, balls, wooden train sets, water and sand toys. The list would include any toy a child used their own intellect and power to use.
Children love to learn by a variety of experiences at this age. Starting a play group and taking turns meeting at other children's homes is a wonderful way to provide different learning experiences.