Depending on your needs, Arduino may be a fun starter kit with lots of shields (hardware expansions) available and a huge community. Arduino has a low entry level from both a hardware and software respective and you can still write regular C/C++ with it.
However, Arduino doesn't have a debugger. Recently Atmel has released AVR Studio 5, which is integrated into Visual Studio. It makes it even less portable to OSX, unfortunately.
I do know microchip has released MPLAB X final recently, and it is supplied for Mac OSX out of the box. I don't have a Mac to test it , but I am pretty certain it will work (have seen 1 or 2 random video's of people using it fine with Pickit 3 and PIC24's).