I used to do the same when I joined, just to get the initial set of orders in. Overtime, I figured out a slight pattern in the bursts of Requests (for me it was usually around Noon and Evening). Then I just used to check around those times and send offers. Also, I always used to pick the ones that had a few key things about them:
The budget. For me it was always minimum 30$, anything else I didn’t even bother.
The quantity (and quality) of information provided by the buyer. I always used to chose the ones who described their needs clearly. This just might be me but I felt that these kind of buyers would actually put in time to go through the requests and read the ones that actually put in effort. That being said, I always custom wrote my offers, making sure to include parts of the buyer’s own information.
Just the overall language style. Again, this is just me but I always picked the ones that were a little more “friendly” in their language. For eg. A simple “Hello!” or a “Thanks!” in the request.
Just a few things I did. I noticed that with every 6 requests sent, I had at least 2 buyers coming back to me.
Now I don’t use buyers request that much as I get organic inquires + lack of time in general.
Your milage may vary
Best of luck!