What are a Gimbal and Tripod used for?
Gimbals are good for adding movement without shake, they're brilliant for run-n-gun documentary work where lugging a tripod slows you down. They're perfect when you're in the thick of things, using a wide lens to shoot close to the action.

They take a bit of time to master, you need to practise steering them and think about the movement. You also need a camera with good autofocus and you probably want to shoot with more depth of field; while you can focus-pull on a gimbal-mounted camera, particularly with a remote motor driven follow focus, it's challenging.

A major disadvantage of a gimbal is that you're limited in terms of the weight of the camera. Unless you're shelling out a lot, the cheaper gimbals are limited to something the weight of a DSLR. So if you're looking at using a cinema camera or shoulder-mount style video camera you're also going to be spending more on your gimbal.

A gimbal is fairly useless if you're shooting interviews, unless you're a fan of the camera-always-needlessly-moving style of interview shooting, and if you are, damn your eyes, you're a disgrace. For static interview set-ups a tripod will win hands-down.

You also wouldn't take a gimbal if you were trying to get shots of snow leopards in the wild, live sports, or candid long-lens documentary footage. You can't really stick long lenses on them, not just because of the weight, but also because even with the stabilisation the constant movement is still too much.

Another consideration is ergonomics. Even though the average video tripod weighs more than the average gimbal when you're lugging it to the gig, once you're there you put the tripod on the floor. Because you have to hold it while shooting, shooting for extended amounts of time with a gimbal can be exhausting. Also, the batteries on a tripod never go flat and the software doesn't ever need resetting.

Finally, a bottom of the range gimbal is going to cost you the same as a pretty good tripod. Worth considering if money is tight. 

TL;DR Both are useful parts of the kit, but they have different uses.