I never thought of getting an apron for my son until I saw him wear one at daycare. It was like a lightbulb went off. An apron will protect his clothes and make cleaning up less of a hassle for me.
My favorite Mimi the Sardine Child Apron is this colorful pattern ot chicks. There are no toxic finishes so it's definitely kid-friendly.
They're priced at $20 and sold at Giggle.