So what is appropriate to spend?

[malaholic]

"Appropriate" is an individual decision.

+1 to that.

I'd leave the "appropriate" and the "first road bike" out of the equation, and then it becomes just like any purchase in that presumably there is some maximum amount that you want to spend, and some minimum criteria you want your selection to meet, and you choose from what fits between based on your own personal preference & goals.