Ahh, grasshopper, you have a few things to learn about: GAS (Gear Acquisition Syndrome), The endless sensor envy argument (full frame vs APS-C vs Micro Four/Thirds vs...) and the truth that there is a purpose, time, and place for everything.
First, know that GAS is an incurable disease. Once you catch it, it will cause you to make purchase after unnecessary purchase, all in search of product nirvana. It does not matter whether it is cars, cameras, computers, shoes, socks, baseball caps, or 1960s transistor radios, you will have to have what you don't have. NEVER MIND the fact that the purpose of owning something is to go out and use it until it falls apart or you die trying to kill it! GAS causes you to be BRAND LOYAL (Ford vs. Chevy, Mac vs. PC or iOS vs Android, Canon vs. Nikon, Nike vs. Adidas, etc.). You wind up spending hours in forums, dissecting the finer points of this or that release. Meanwhile, life passes by on the street in front of you!
Please watch this YouTube video from Zach Arias:
https://www.youtube.com/watch?v=PHYidejT3KY I think he sums up the whole futility of the full frame vs APS-C argument nicely. FUGGEDDABOUDIT.
Yes, full frame cameras play important roles in the photography world. So do all other digital camera formats! But the idea that full frame is some sort of digicam nirvana is pure crap.
Look, I've used every film format from 4x5 inch view cameras down to half-frame 35mm. That's 4x5, 6x17cm, 6x9cm, 6x6cm, 6x4.5cm, 70mm full frame long roll, split 70mm long roll, 46mm long roll (four variations in negative length), 35mm unperforated long roll, full frame and half frame 35mm perforated (size 135). Every one of THEM served a different purpose, Every one of the cameras used to expose them had a long list of positive and negative attributes.
The same is true of digital cameras. There are medium format digital backs for medium format cameras. They cost tens of thousands of dollars and are used by only a few photographers who live in rarefied air. They are well suited to advertising photography. Any time you need a super-high resolution point-of-purchase display, they are a good choice.
There are full frame cameras advertised for "pros" (Nikon D5, Canon EOS 1DX Mark II, etc.) and "amateurs" (Nikon D750, Canon 6D, etc.). There are lots of in-between models. There are 50MP Canons and 36MP Nikons and 20 MP Canons and 20MP Nikons, all full frame. The differences are important for the specific user crowds they serve. Add megapixels, and you gain resolution, but you also lose dynamic range, high ISO performance, and high framing rates for sports, wildlife, etc.
In each of the smaller sensor families, there are similar variations on the same theme. Life is full of little trade-offs. As camera sensors get smaller, the lenses (can) get smaller for the same fields of view they cover. The 12-35mm zoom on my LUMIX GH4 is 1/4 the size, bulk, and weight of the full frame 24-70mm lenses it emulates. That's great for travel and fatigue reduction. But as cameras get smaller, packing the same number of pixels onto smaller chips changes things. Some things change for the better in some circumstances, while some things change for the worse.
Again, I would encourage you to work with what you have. Learn the principles of photography, and how to manipulate ALL the variables. Once you've recorded your 10,000 first images, you'll have a MUCH better idea of what gear you need, exactly WHY you need it, and you'll make a more intelligent decision about it.
Don't let anyone tell you you need something, just arbitrarily, "...Because it's the best." Always ask yourself, "Best for what?"
Ahh, grasshopper, you have a few things to learn a... (