As a newbie you should see the well reviewed girls. If you must use the agency, see the agency girls that have reviews. If you keep using that same agency, once you have a relationship with them, and have seen some of the well reviewed girls, it may be okay to see one of their new girls. The agency owner will want his/her new girls to get good reviews, so they may encourage their regular customers to try out the new ones, and report back, and if service is not up to par, they may offer discounts on future services or something. Of course this is talking about good reputable agencies. And in any case you are not that "established customer," so don't see the unreviewed new girls!
Be safe. Have fun!

I have done this many times with good results.  I would not do it if she just started with the agency however.  Wait until she's been around long enough for the agency to get positive or negative feedback on her.  A reputable agency will not represent a lady that people are complaining about.

was with an agency girl who had only a handful of reviews and some were lukewarm.  But I loved her pix so I did it.  Big mistake.  Now that I'm more experienced and known to the agency I can ask about the new girls and get good guidance.  Since you're not in that situation, I'd stay away.