Buy phone gimbal or DSLR gimbal?

I'm looking into buying my first gimbal. I've pretty much decided which one in either category I would be buying. I've only been into photography/videography for about a year. Here are relevant things I have:

Dji Phantom 3 Pro
Nikon D3200
3 lenses (2 kit, 105mm Macro)
Tripod
Galaxy S9
Adobe Suite (all apps)

I'm wondering would it be better to exclusively use my Galaxy S9 and buy a phone gimbal? Or should I buy a DSLR gimbal so I can use the bigger camera? With the DSLR gimbal, I should be able to attach my Galaxy S9 with some adapters. Is that a better idea?

Go with the DSLR gimbal. As you stated, you can use your cell phone on it with an adapter. With a cell phone gimbal you'd never be able to attach a DSLR onto it because it woudln't be able to support the weight. Also, over time you're going to change your cell phone a lot more often than you'll change your camera, and you may end up with a phone that doesn't fit on the cell phone gimbal any more, while with the DSLR gimbal you can just get a new inexpensive adapter if necessary. And when it comes to filmmaking, as your skills and talents improve for making better videos, you'll get much better quality out of your DSLR than you will with a cell phone. The censor is much bigger to give you much better light gathering capability, and you can change out lenses to get different looks, which you can't do with a cell phone (you can get clip-on lenses for a phone, but their quality is mediocre at best).

What are your needs? Why do you think you need a gimbal at all?
I assume it's for making videos, but you can get just as good results with VR lenses.
Personally, I would never recommend a D3200 for video at all. If video is a big deal for you, you'd be better off upgrading to a D500, or dumping Nikon for Sony or Panasonic instead. Nikon's video performance is notoriously awful!