Wasim: Welcome to the board ! We're usually a friendly bunch, so ask away. Besides that, sit down, hold on tight and enjoy the ride ;-)
About your question:
The shape of the pipe will do more about what "cut" of tobacco you'd smoke. Opinions vary wildly. Some like flakes in narrow bowls, some like flakes in wide bowls (Like me).
Dedicating a pipe has more to do usually with the "blend" and flavor of tobacco. For instance, I have pipes dedicated to aromatics and those in which I will smoke non-aromatic tobacco's only, usually Virginia/Perique blends. You don't want to have a lingering vanilla or rum or chocolate flavor when you are smoking a straight nice peppery or smokey tobacco. So that's where the dedicated pipe usually comes in more so than dedicating it to a flake or ribbon or kake tobacco. After all, you can get a heavy Latakia or a full Virginia in a flake as well as heavily flavored tobaccos in a flake. You don't want flavors to mix too much.
I have done the same tobacco (Escudo) in both narrow tall bowls and squat wide bowls. It just gives a different flavor pattern, but it works either way for me.
For a a 320, which I believe is a relatively squat wide bowl, I'd go with Schmitzbitz' advice. Start with a good ribbon style tobacco since they're easier to smoke.
Non-aro recommendation: Perhaps a GL Pease Stratford. Some may give you a Latakia blend, which I personally don't care for. But there's good ones out there.
Light aro recommendation: I would go with the trusty 1-Q or MV-1000
Heavy aro recommendation: I would head for MacBaren Vanilla Cream Loose Cut (which to prove my example above also comes in a flake cut, so make sure to get the Loose Cut).
But it'll depend greatly what you have or what you have access to.
Hope this helps
Good luck.
