I'm very new even for a newbie, both with Lexus and with a hybrid car.
The type of driving makes an incredible difference to consumption.
On the motorway the fuel consumption is similar to any other large car, but in the city as long as it is not too congested and that you can keep recharging the hybrid battery you're laughing. Once, when things were at a standstill and my engine came on to charge the hybrid, things got painful.
My 2012 RX450 h over 8 fills has varied from 33.0 to 28.9 mpg with a lot of motorway driving.
May I suggest you have a look at Fuelly -and maybe join in-
http://www.fuelly.com/car/lexus/rx450h/2013