Reddit mentions of CAMVATE V Lock Mounting Plate Power Supply Splitter with 15mm Rod Clamp

Rigging it is easily the best way to make it usable for sure. The downside to rigging is that it gets bigger. (which for some is a downside, not really for me)
I'd start with the camera, if you're running just the camera I'd look at the smallrig cage. I've been really happy with their stuff. I would however take a look at what you're rigging onto it and ask yourself which cage to get, they have the gh4 cage, but they also make a "universal" small dSLR cage. I personally like the universal style (though I've not used it so take it for what its worth) because it has a clamping plate on the bottom and a hot shoe clamp. this secures the camera to the cage in 2 spots. I like the rigidity. (but I run heavy stuff on my rigs).
If you are running the GH4 with a YAGH the only option is the Wooden Camera kit. I've beat mine for 3 years on the road and its great. 100% recommend it. I went the YAGH rout because I was dropping this into a production environment, I needed the SDI out, XLR in and audio DAC, as well as teh TC for multi cam sync.
Now regardless of what cage you get the next and most important thing you can buy is the HDMI cable clamp. Dont skip this. if you want to use a monitor you'll need an output. I don't really care who makes the camera they all are flimsy and break. they are all expensive to have repaired. and Panasonic isn't repairing GH4s anymore to my knowledge.

Next I'd look at mounting. what are you putting the camera on? Its nice to set cameras down from time to time, even if you're just shooting handheld B-roll. I'd look at the CAMVATE quick release mount base. For like $40 you you get quick lease plate for your cage setup and a height adjustable rod clamp. you can then throw any tripod plate on the bottom of it and you're up and running. The rods give you the starting platform for future rigging.

With the camera now in a cage and on sticks. I'd look at a top handle. I'd get a smallrig again, but one with a nato slide. quick release is always the best option. so figure about $15 for the nato plate and then $60 for a handle. I like the handles with rod mounts so you can run an evf on them. I also would stay away from handles with leather or leather like wraps. they get hot and slippery with sweat.
alright we're getting there. this is where it gets more use case specific, what kind of audio are you running? also what kind of batteries are you running? and then do you use an external monitor or an evf?

For audio, if you're running externally, I'd look at getting some sort of battery plate that you can mount the audio to. CAMVATE again has a nice setup for a Vlock battery with all sorts of various regulated power on it. Its also built on a nice cheese plate.

After that, I'd look at a mattebox, then a follow focus, then monitors. but that gets pricey very quick.

so for links to everything:

Cage - $70.00
Rod Base and riser - $39.00

Nato Plate - $13.00

Top Handle - $60.00

Battery Plate - $100.00

Rods - $13.00

The last thing, if you have a monitor that you want to run on the rig, don't waste your money on the friction arms. they fall apart so fast. for about the same cost of a manfrotto arm you can get one of smallrig's double ball arms. I run this like 3 times a week and its great.

Monitor Mount - $50.00

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So all in total you'd be looking at about $300.00 and you'd have a solid base to start working with. You can probably do better digging around on amazon, or even going to ebay. but I don't have the time right this second to do that. but when you are looking at things make sure that everything is either quick release or thumb screws. trust me you do not want to have to carry a set of allen wrenches to build your camera every time.