If you have a C harmonica what 2 or 3 harps should you get next for playing the blues?

After a C harmonica, consider getting an A harmonica and a D harmonica for playing the blues. The A harmonica is great for playing in the key of E, which complements many blues songs, while the D harmonica works well for the key of G. These keys will expand your playing range and allow for more versatile blues improvisation.