I have a Norco Katmandu that has shimano tourney derailleurs and shimano shifters which are low end. I am looking to upgrade some parts to make the bike work better and am wondering where is the best place to start to get the best bang for my buck? I do some road driving and some off road but not enough to justify buying a new bike. I was thinking of getting a new rear derailleur but someone was telling me getting new shifters may be the best place to start. Any input would be appreciated

You can usually get a package price on shifters and derailers. I think you will notice a big difference. How old is your bike? What kind of brakes do you use?

If your bike has Tourney components, then normally it will be cheaper to buy a complete bike rather than replace parts like the shifters. The Tourney on your bike is most likely 7 speed (this model last had Tourney spec'd on in 2008, and was 7 speed), and upgrading to anything which will give better shifting, will require an upgrade to either 9 or 10 speed, as parts just aren't produced for the mid range in 7 speed now (there is the possibility of NOS parts but you can't just pick thee up at a bike shop).

If you are having issues with your shifting, would be looking at why; at the cables, routing and RD hanger, are all these good / aligned? before spending any money on new parts like shifters and RD's.

My bike is old, 2006 but the frame is still in good shape. The front has disc brakes hayes mx 4 rotors and v brakes in the back. Is there a good place online to find the shifters and derailleurs? If i don't get a package and get one at a time what should be the first thing i replace? Thanks for the input.

Yes it has tourney components and is a 7 speed. I know someone and may be able to get a cassette that is either a 9 or 10 speed. If i am able to do that would it be worth upgrading my bike? I don't want to spend a whole lot of money. My bike shifts fine i am looking to get something that is just smoother works a bit better.

Some online retailers I like include

blueskycycling, pricepoint, huck and roll, jenson and nashbar. You can also check around for bike clubs in your area. There may be people with used parts that they will let you experiment with. That way you can get an idea of what works and not. Putting a 9 or 10 speed on a '06 might run into some problems, maybe not. Tweaking bikes is part of the fun in the game. Enjoy it. Wish I could be more help. Best I can say is get the rear cassette, Rear D and shifter all at once. Match the eqt as close as you can.