Second an IDE or text editor you can live with - you will going to use this a LONG time (maybe for your whole development career!), that’s why Emacs and VI are so popular still, they don't change all that much. Having to switch IDEs/Editors after you’ve got into the groove will make your development stride stumble greatly. Beyond that it's up to your desires, some people live by sublime, I can't get over it not being able to print (really!?) Anyway, no one editor or IDE will please everyone, so dont be reluctant try out demos till you feel satisfied.
MAMP is really nice in that its interface lets you redefine web root on the fly which works if you got a bunch of similar projects.. Though sub directories are what most do otherwise (unless the platform is really specific about file placement in relation to web root)
So, for me I'm on Aptana (IDE; based off of Eclipse but PHP tuned) on Linux my web root on my dev system stays constant, and projects just get various subdirectories and different MySQL dbs. Working with lots of projects is one of those things ya gotta work through and learn, best tip - learn to do backups/restores.