The "order" of engine improvements is a somewhat difficult concept, as they are all interwoven.....and they need to work together to improve the ability of the engine to breath. The improvements are also directly tied to your mechanical ability....and your wallet.
Everyone agrees that the muffler and refined carb jetting is the first step in making the engine run better.
Beyond that - it gets far more complicated.
The high compression piston has the most bang for the buck in my opinion - however a cam swap really brings it to life...and while the head is off it is a good opportunity to open up the exhaust port a bit. This labor intensive and parts somewhat expensive......if you have a piston or cam failure it is easy to justify the upgrade. It is somewhat harder to justify taking a good running and reliable engine apart just to get a few more HP.
A cam swap by itself provides a worthwhile improvement, and you don't have to remove the engine from the frame.
The stock carb works OK, and it can even work OK with a modified engine. I ran the stock carb for a year with my 95mm Wiseco and Stage 1 Cam engine, and it did just fine. When I switched to the Mikuni VM carb I didn't notice much of any power increase - what I noticed was a more responsive carb - things happened a tiny bit faster when I moved the throttle. The Mikuni is not a constant velocity carb, and it doesn't have a TEV valve to help with the rumble if you close the throttle while decelerating or shifting - so you have to become a better rider and learn how to operate the throttle to cut down on the backfire while coasting or shifting. It does take some mechanical and jetting skill to get this right.....and the Mikuni is not a "bolt in" for connection to to the stock air cleaner - so you will either have to adapt plumbing or use a different air cleaner. (I use a large foam air cleaner). I really don't know how much difference a carb swap will make on a stock engine.
Here is what the "forum" has been recommending for the order of improvements in the Tech Section.
http://suzukisavage.com/cgi-bin/YaBB.pl?num=1291516932