Buying components separately is cheaper, though sometimes there are good deals on pre-builts.
Choosing the right components can be a bit tough, it all depends on your budget. That's the first question. If you're buying it for Christmas you may want to wait for black friday and buy then.
The market is still kind of in shambles. Everything is a lot more expensive than it should be because of parts shortage. If you're looking for mid-range I'd recommend a GTX 1660, but if you want to spend a little more and future-proof your PC, I'd recommend an RTX 3060.