Bought tickets on the day at 9am (joint ticket with the colosseum) no queue at that time. Got half price as under 25 ticket (need to show ID for this) .
The whole place is amazing with loads to see . Spent 5hours here.
There are lots of water fountains around (which are all drinking water unless otherwise stated) .
There are many information boards telling you the history of the place (English/Italian only) .