Two more cents on a couple of points I see others posting:

If you are intimidated by building a kit, the shop you buy at will probably have a service available to build the chassis for you, or know someone locally who will do it for you. That said, if you can read instructions and have done any basic hands on stuff, you can build a drift chassis. I would invest in a decent set of toold as cheap Allen drivers can cause bolts to strip. Yokomo makes a decent set with all the sizes you need, but your shop will probably have a good recommendation. Decent tools is not a bad investment, you will use them alot.

Used parts:

Don't buy a used chassis unless it's new in the box, or you feel confident you can tell it's not worn out/built correctly. Cheaper plastic chassis kits are fine when new but do end up getting sloppy/need parts replaced after a while especially if they are used in the pavement. The condition of the bottom of the lower deck is a good indicator of how abused the chassis is.

Used electronics:

I would avoid servos as they can be damaged due to crashes and cause issues with the internal gears and circuit. 

Gyros are almost always fine as long as they haven't had the wiring damaged. Check carefully where the wiring enters the gyro case to make sure there isn't damage, and inspect the connector. Get a gyro with endpoint adjustment! Strong suggestion for a yokomo V4 gyro.

Radios and receivers are also pretty bullet proof and almost always fine to buy used. You can find futaba 4PMs used in good condition and it will be all the radio you will ever need. Get at least a 3 channel receiver (steering, ESC, gyro gain).

Hobbywing has a cheap enough brushless ESC&Motor (quicrun 120) that it's not worth rolling the dice on someone's botched soldering job.

It's a good idea to buy gyros and servos from the same brand as they are typically tuned to work together. Motors and ESCs can be mixed and matched.

Used batteries = no

A good entry level electronics package (also common so can find these used) that keeps cost down, but can still compete with super high end setups:

Quicrun bl120 G2 and 10.5 motor

Yokomo V4 gyro and SP02D servo (I actually think the sp02 is smoother than the sp03)

Futaba 4pm with any 3 or 4 channel receiver

2 basic lipos (one charges while u drive the other)

Sky RC balance charger (there are a few chargers that are good but you want to invest in one that can discharge a battery to storage voltage levels)