Hi There & welcome to KentScoobies - would you like me to add you to our mailing list so you are kept up to date on meets & events?
Now to answer some of your questions....
Tyres - I think you will find most people favour Toyo Proxies for handling & grip, they are not too bad for wear either - as for price, it depends what size alloys you have....
Disks and pads - the only way you will get better braking is to change your calipers to 4 pots, not combination of disks and pads are going to be any good on Subaru 2 pots.... Also, EBC greens are no good for Subarus, you should go for the reds, or Pagid blues. I have 4 pots with Pagid blues & EBC dimpled & grooved disks, and I've stopped a lot better since I had 2 pots before & I had to start braking at the beginning of the road to stop at the end lol
Turbo heat shield vibrating is a very common problem, best fix is to remove it completely....
As for handling, yes lots of practice is a good idea to start with However, take it to Elite and get the laser alignment and the Prodrive settings, you won't be dissapointed, my car handled like a completely different car once I had this done.
Hope some of this helps, I'm sure someone else will be along with other ideas
Pele