Kids take joy in exploring and are learning concepts. The more we involve their senses in the process the more concrete the experience is, making learning easier. Physical toys are important at this stage. Ring toss games and ball toss activity centres are great fun, and vehicles continue to please. Of course, a place to run, jump, climb, and swing is a necessity.
Creative toys are as much fun to buy or make as they are for kids play with.
Several hundred tons of play dough is nice. There are many games that incorporate learning the alphabet, colours, numbers, or shapes. Ask people with kids what games they enjoy. Buy those, and play them with your kids. You can use them for colour sorting or having your child reproduce patterns that you've made.