2nd Harmonica

A C harp (a harmonica in the key of C) is fine for your beginning bending explorations. Only the highest notes (Holes 7 thru 10) are easier to bend on low keyed harps like a G. The low notes might actually be harder on a G. (That said, everyone's oral geometry is different, and what's hard for one might be easy for another for that reason.)

I started on a C harp like most folks, then got an A, which is great for blues in E. When I first got a G I found it kind of daunting because the reeds responded so differently. They seemed kind of sluggish and slow to react. (The reeds in a G harp aren't much bigger than those in a C harp, but they have more weight on the ends so that they'll vibrate at a slower rate.)

I'd evaluate which key(s) to get next in a couple of different ways:

1) What keys are you most ikely to be playing in? Get the harps that will play in those keys, because those are the ones you'll use the most. (I assume you know about second position, where instead of playing the harp in its labeled key you play it in a key five steps up the scale, and use the draw chord in the first four holes as your "home" chord. For instance, you'd use that C harp to play in G).

2) Which keys will play similarly to the key(s) you're already familiar with? For instance, a G harp might be a big leap if you've only played a C harp. You might step down to that via an A harp (or perhaps also a Bb harp). And you could move up into the higher keys with the same approach: after a C harp, get comfortable on a D before going up to Eb, E, and F.