Change my GPU or change my PC entirely?

[Artorius]

The interface used for graphics cards been the same for a while now, what they're trying to tell you OP is that you can buy your graphics card upgrade now and use it with your current pc, then you upgrade the rest later. Which would probably be more money effective than buying a subpar card just as a placeholder.

[Potrice]

So slowly and gradually upgrading everything is better than selling the pc for like 600$ and use that money to buy something new? If that's the case, then I'll buy everything gradually.

[Artorius]

So slowly and gradually upgrading everything is better than selling the pc for like 600$ and use that money to buy something new? If that's the case, then I'll buy everything gradually.

Well, the only thing that you can use on both different platforms is the graphics card and the power supply (apart from HDs/SSDs obviously). The PCI-E slot is virtually the same.
You can't for example upgrade the CPU only because you'll need a different socket, which implies that you'll need a different Mobo, and memory too if you go DDR4.
Keep in mind that triple channel isn't used anymore so you'll lose this too if you choose to remain using your current memory, good news is that this doesn't make any almost difference.

So, you'll have to upgrade CPU + Mobo + RAM* together. The rest can be done separately