As of January, Hagia Sophia is now 25 euros to enter the upper level where you can look down. The main level is now off limits to visitors 24/7. You really miss alot here and I don't know if its worth the line and cost. Expect lines to get the tickets here and guides can't skip the lines here. I don't think guides are even allowed inside now and you need a scarf which they sell for 30TL. There will be people selling tickets to those in line at a slightly higher price if you don't want to wait in line. Make sure to note the prayer times for the Blue Mosque so you know when to go and the visitor entrance is not inside the courtyard but outside to the right as your facing the entrance. Cistern will have a long line as well unfortunately and this is really the only place where having a guide would help as they can skip the line. Istanbul is very walkable even without the tram. Make sure to leave plenty of time for the bazaar, its big and don't worry about getting lost. If you do just ask someone where the exit is or walk until you find the outer edge and follow it til you see exit.