I wouldn’t really say that you would be settling for an older Ninja, really they are good bikes. The older bikes have good power, are nimble and get awesome fuel mileage, also I believe they have a little more room. The newer one’s do look better (I think at least), have a stiffer suspension and (according to Kawi) have more ‘usable’ power, however they cost more and don’t get the same mileage.
It depends on how you are built, how much you want to spend and how you are going to ride it. If you are never going to push the bike hard, the ’07 and older will be great, however if you plan on taking it to the limit every chance you get maybe the ’08s and newer are a better option. If you are a ‘heavy’ rider you may want to consider the newer model, but the older model can handle it. It you are tall, maybe the older model will fit better than the new.
$2300 for the ’06 or ’07 isn’t a bad price, but if you are willing to go a little older, like with an ’04ish I wouldn’t be surprised if you can find a gently used one for around $1500, but I have seen ’99s going for that on craigslist here…..
For gear, it depends. For the helmet I would suggest going somewhere local that has a decent selection or two or three different local shop. I don’t care what anyone else says, you have to try on a helmet to see how it fits. For the rest of the gear, you can get it online (Motorcycle Superstore, among others), at a local Cycle Gear (if there is one near you), or at a local motorcycle dealership. I got all of my gear locally, mainly because it is my first set of gear and I wanted to make sure that I got stuff that fits how I want it to. You can save a lot of money buying closeout merchandise.