You only really NEED a FF camera if:

You are a pro and make your living with clients demanding the absolute best IQ (some will demand medium format - commercial ad or fashion photography!)
You are a wedding photographer and need to shoot the lowest possible noise level inside churches, for example, or other indoor shooting applications.
You are a landscape or portrait photographer (although APSC does a great job there too).
You shoot a lot of superwide angle subjects, real estate interiors for example.

FF will give you about 1.5-2 stops extra margin for acceptable noise levels. If you shoot at ISO 6400+ that will come in handy.

Everything else is a want...but we all experience GAS at some time or another. Keep in mind FF will demand great quality FF lenses, which are larger and heavier generally at the same focal ranges and f number. If you are a casual daylight shooter - like me - APSC is fine. I have the D7200 and it takes great photos with good noise control under ISO 10,000, especially in daylight, and sometimes up to ISO 18000. I use mostly FF lenses, anticipating my upgrade to a D850 or other FF body....I will still keep the 7200 for applications where a DX comes in handy, but the D850 also has a not too shabby DX mode 19.4 MP.

As a beginner, I would recommend you buy an APS-C or micro 4/3 format camera instead of full frame. Unless you make really big prints (16x24" or larger), you're unlikely to see any difference. The vast majority of users, the smaller sensor cameras are all they really need. In fact, I'd wager a lot of people who spend serious money to buy full frame gear and make a lot of effort hauling it around never actually see any "real world" benefit from it. Sure, they see sharper and more detailed images on their computer monitor while viewing them ridiculously large "at 100%". But they're the only person who will see their images that large.... by the time they've resized for prints or online display, the rest of the world will never see all that "full frame goodness".

A full frame camera is typically bigger, heavier and a lot more expensive. Not ideal for travel, due to size and weight (been there, done that!).... and 2X to 3X the price of cameras that use smaller imaging sensors. There's also less lens selection... a full frame camera basically requires full frame-capable lenses... while the smaller sensor cameras can use both those same full frame lenses AND lenses that are made specifically for them (and are smaller, lighter, less expensive).

If you plan to travel a lot with the camera, look for something reasonably compact and lightweight. For example, Canon offers a Rebel SL-2 (called an EOS 200D outside N. America) that's quite capable and full featured, but weighs just over 14 oz. and is reasonably affordable at about $600, with EF-S 18-55mm IS STM "kit" lens (weighs 7.5 oz.). That's a 24MP, APS-C sensor camera.

In comparison, the least expensive, smallest, lightest Canon full frame DSLR is their EOS 6D Mark II, which is currently selling for $2000 with EF 24-105mm IS STM "kit" lens. That camera is 24MP, weighs about 24 oz. and the lens weighs another 18+ oz.

Further, there are currently almost 90 lenses in the Canon system to choose among, all of which will fit and work on the SL-2. In comparison, with a full frame camera the selection is still good, but reduced somewhat to around 78 full frame compatible "IF" lenses. The other lenses are "crop only" (Canon calls them "EF-S").

I'm using Canon examples because that's the system I use and know best. But you'll find similar in Nikon, Pentax and Sony systems. (Nikon has similar range of camera and lens selection.... Pentax and Sony each have about half or less the number of lenses available.)

The above are DSLRs or "digital single lens reflex". They have an electro-mechanical shutter and a mirror system that redirects the through-the-lens view to a viewfinder (the also can give Live View on their rear LCD screens). An alternative that can be even more compact are "mirrorless interchangeable lens cameras" (MILC). Sony makes those in both APS-C and full frame sensor formats (they are essentially phasing out DSLRs). Fujifilm and Canon both make APS-C format MILC. Olympus/Panasonic make MILC too, using slightly smaller "micro 4/3" image sensors that allow their cameras and lenses to be a tad smaller and lighter.

MILC are a relatively new type of digital camera.... First introduced around five or six years ago. Because of this, there's somewhat less selection of lenses for them. For example, Canon only has 7 or 8 lenses for their M-series, so far. Fujifilm has one of the largest selections of lenses, with roughly 30. Sony and Oly/Panasonic are close to that number too. Nikon recently discontinued their MILC system ("Nikon 1", used a "CX" sensor that's smaller than anyone else), but has stated they'll be introducing a full frame system soon. There's no indication that Nikon will offer an APS-C MILC. Canon has committed to introducing a full frame MILC soon, too... but has continued to offer APS-C models. Pentax has just been quiet when it comes to mirrorless... they offered one briefly (which was unusual in that it could use their exiting lenses, didn't need special ones designed just for MILC). With Pentax now owned by Ricoh, I wouldn't be surprised to see them introduce a MILC in the future, but am not holding my breath.

MILC have some advantages.... and some disadvantages compared to DSLRs. One advantage with the APS-C/micro 4/3 models is smaller size and less weight (there's a little, but not much size/weight advantage with full frame MILC). The models with one use an electronic viewfinder, which can be useful in low light conditions or to help when using manual focus lenses, but draw a lot of power and may have some time lag. Folks shooting sports/wildlife and other action photography still generally prefer the optical viewfinders used in DSLRs. Another is the more limited lens selection for MILC, as already mentioned. OTOH, it's possible to adapt many lenses from DSLRs and vintage systems for use on them.

Perhaps the biggest consideration... Despite some short-comings and limitations, a lot of buyers think MILC are the "latest and greatest thing". As a result, they're typically selling at considerably higher price than comparable DSLRs.

Finally... Folks tend to get all caught up in the camera and it's features. In truth, the lenses you use upon it make a much bigger difference in what you can shoot and the quality of your images. Even the least expensive cameras are quite capable.... for example almost all the Canon APS-C models use essentially the same 24MP sensor: entry-level T7, extra compact SL-2, slightly larger and more full featured T7i, next step up 77D and even more advanced 80D. In fact, in Canon's current APS-C models, only the top-of-the-line and most pro-oriented 7D Mark II uses a different sensor (20MP).

To some extent, I'd recommend most people spend less on the camera... more on the lenses they use upon it. This doesn't need to "break the bank". Again using some Canon examples, if you wanted something a bit more advanced than the SL-2... pick among T7i, 77D and 80D Canon. The EF-S 18-55mm STM lens sold in kit with some of those is pretty plasticky, but a decent, inexpensive lens. Their 80D is often offered in kit with the somewhat better EF-S 18-135mm IS USM lens. This adds to the cost, of course.... $1300. But that may be money well spent if it helps avoid needing to "upgrade" lenses a year or two in the future.

Beyond the basic "kit" lens bundled with the camera for some discount, it will depend upon what you want to shoot. If you want to shoot landscapes a wide angle lens might be nice and there are two very capable Canon lenses to choose between: EF-S 10-18mm IS STM for under $300 or better built but slightly bigger and heavier EF-S 10-22mm USM for about $600. Or maybe you want to shoot portraits, in which case an EF 50mm f/1.8 STM for $125 or an EF 50mm f/1.4 USM for $350 may be a good choice. Or you may want a telephoto for sports or wildlife, and again have a number of choices including affordable EF-S 55-250mm IS STM ($300), a bit more upscale EF 70-300mm IS USM II ($500), more premium build and high performance EF 70-300mm "L" IS USM ($1350), high premium EF 100-400mm L IS USM "II" ($2000) or even ultra premium EF 200-400mm f/4L Extender IS USM ($11,000). Or maybe you want to shoot macro, in which case there are five options. There are also a wide variety of other types of lenses available from Canon... as well as Sigma, Tamron and Tokina lenses made for use upon them.

You'll find similar from Nikon, if you prefer. I've noticed Nikon cameras and kit lenses tend to be slightly less expensive than comparable Canon... But Nikon lenses and accessories that you might want to add tend to cost more than the most comparable Canon. Also, the more entry-level Nikon D3000-series and D5000-series cameras require AF-S or AF-P type lenses to be able to autofocus. Some other Nikkors (AF, AFi) will not be able to autofocus on those cameras (requires D7000-series and higher models), but can be used manual focus.

Have fun shopping! Go look at some cameras in stores... handle them and see if one or another "feels" better to you. If possible, turn them on and check out the menus to see if one or the other seems easier and more intuitive (some get high marks.... others, not so much!). No doubt you can learn to use any of them, but some may be easier than others. Also look at support such as guide books, warranties and service departments (which hopefully will never be needed). If you have friends or family who will be helping you, it might be wise to get gear that's compatible with what they have, so that you can share.