This verse tells us that even Simon accepted the faith and let himself be baptized! He is amazed by what Philip says and does. The idol of Samaria becomes a follower of Jesus. Isn’t that the best advertisement for the gospel of Jesus?
But Simon must still learn who the Spirit is. He still thinks he can buy the Spirit with money. The reaction of Simon (in Acts 8:19) betrays that he is still too attached to superstition.
13 Even Simon himself believed, and after being baptized he continued with Philip. And seeing signs and great miracles performed, he was amazed.