How can one make friends at 30 years of age?

pay the freight, don't be a tight-wad

Be friendly. Say you're at a book store or something and you see someone looking at content that you know about. Ask them questions about it or start a conversation. That can usually lead to you exchanging numbers.

Go into steam spas

there is no age limit for making friends, you can do different activities and find new friends that way.