Lapel mic can work. It's the simplest, but I hate wiring people up each time. One of these powered ones can go straight into a GH4 https://www.amazon.com/External-Microphone-Accessory-R500-R600-R700-R800-Camcorder/dp/B00UXNZ1BM/ref=sr_1_10?keywords=powered+lav+mic&qid=1552942515&s=gateway&sr=8-10.

I prefer using a shotgun mic on a stand though - particularly if I want to save time not wiring the subjects up. Set up the mic so that it is right above their head out of the shot, pointing towards their mouth/chest area. Mic stand, Cheap shotgun mic (I'm not sure how you'd mount that mic on the stand though - may need some sort of adapter. I use a stand like that, but a phantom powered shotgun mic into a recorder.