OK now the list of attractions on TA is confusing because Numbers 2,3,4 and 5 are all in No 1 the Square of Miracles which is one large field that contains the:
Duomo (cathedral) 9/10
the Campanile (the cathedral's free standing bell tower), 9/10
the Baptistry, 5/10
the Camposanto, 5/10
and of course the Leaning Tower (dont bother climbing up it for 15 euros as there is not much to see around anyway)
Now the only place above worth going into is the Cathedral itself and its only 2euros to enter and the inside is actually much nicer than even Florence Cathedral. Everything else in the square of miracles is 5bucks (or you buy multi entrances) and not worth it, just see it from the outside.
In other news... there is nothing else worth stopping for in Pisa its actually very run down... escape off to Lucca or Cinque Terre nearby and remember you do not have to go back to Pisa Centrale station (20 mins walk) when you can just go to Pisa S Rossore Station 5 minutes away from the square of miracles and get the same trains mostly everywhere.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.