The problem with those gimbal is that depending on the mobile phone you have, the microphone port might be right against the gimbal making it difficult to plug in an external microphone unless you use an 90 angle adapter with some cables.

I'm personally using two mics:
- the Zoom IQ7
- Rode NT1A with an iRig-Pre to connect it to the phone

Rode does make some nice mobile phone mics and the directional one is a good idea for recording outdoor as it reduces the ambiance noise by focusing more on you.