Vortex Sound Research

Hey....so I have a volca drum, a Td3, a Korg R3 (with usb midi) and a Korg ms2000, and an iPad......Im not sure I have a routing that works. I'm trying to use the drum and the Td3 as my percussion and bass, and the other two as a mix of harmony, melody, or leads, or have the td3 sequence one or the other, and use the other for leads, etc. How would you all connect them together through midi, or would you connect them all and leave some unconnected. Any help would be appreciated.