Appropriate is whatever you have to spend. If you don't love what you buy, you won't ride. If you aren't sure what you want, you may spend too much and still not ride.
Rent. Borrow. Research. Buy what's right for you, not what everyone else has/or what the bike shop is trying to sell. I bought a new hybrid, but ended up upgrading to a road bike within a year. Do I regret it? No. I wasn't ready--and you can always find a new home for a bike 
It's very important to get the right size--a bike that fits you. However, my first road bike came from Craigs List, locally for $50. I needed to know if I could comfortably ride in that position (I have a bad back). I could. My husband loved the bike--took it to work as a "run around" and ended up sending it home with a coworker, for HIS wife. Wish I still had that one!
My brother-in-law's first bike came out of a dumpster. My sisters from a garage sale. Once they started riding, they knew what they wanted to move to (BIL--my DH's old street bike. My sis--my old hybrid).
"Well-behaved women seldom make history." --Laurel Thatcher Ulrich
'09 Trek WSD 2.1 with a Brooks B-68 saddle
'11 Trek WSD Madone 5.2 with Brooks B-17