Honestly, $200 really doesn't buy much, but I can break things down into what they cost for me:
My tank and stand I got used for $200, a 75 gallon
My light was originally $90, but it sucks. I can get a great deal on a 6 bulb T5 lighting system for $150 (aka my next major purchase, but sadly wont get for a while)
On my 75 I have 2 Aquatop CF 500 w/uv Canister filters originally $130 each.
My co2 regulator was $80. It's a Aquatek.
The co2 tank was $90 for the first time, and will be $15 per refill after.
So off of the equipment that I originally had after the purchase of my tank, I would have to say my light would have been my main purchase. It can still do low lighting if necessary so it's not like I would be stuck in bba hell. My second purchase probably would have been 1 of the canister filters. Although 1 alone is not enough for me to feel comfortable, a canister accompanied by my old hob filters would have made me feel better about my filtration.