I started with the entire DS9 relaunch, which initially was my only goal, since it was my favorite series.
Thats cool, it sounds like you and I have the same reading goals! Reading the DS9 book Unity now, ugh its so good!
In regards to the DS9, did you read them all or stop at Warpath? The last two, Fearful Symmetry and The Soul Key, sound like they take place in the mirror universe and I'd probably prefer to skip those if thats the case.
After DS9 is the Titan series and I'm very excited to start that series!