Salmon are on a suicide mission and need to survive long enough to spawn. You can potentially land them on a light rod, especially if you have a good reel, but doing so means fighting them excessively. An 8 wt. gives you much greater control of the situation, especially if there's a good current, and the shorter fight will be much kinder to the fish. Chums can get pretty big and burly, so this is a reasonable minimum.
A good reel and an inexpensive yet sturdy rod will land you fish. As I've said before, the fish don't give a hoot what kind of rod you're using. However, they will notice the reel when they can't break you off because the drag's too smooth. If the fly's presented well (and that's more a product of the right line/leader/fly combination), you'll hook just as many fish on an inexpensive rod as you will on premium gear. Later on, when you've got more dough, you can buy nicer gear to enhance your personal enjoyment.
If you don't have a lot of cash, you could perhaps buy a big Pflueger Medalist reel (my grandpa caught plenty of salmon on them and they'll still stop a truck). Also, Teton's Tioga is a very good, yet inexpensive reel - if you can find one. Don't, however, buy Okuma - they're ok in smaller sizes for trout, but I tried one of their big reels and blew the drag pawls out on Skagit Chums. :reallymad
Good luck and happy fishing. :thumb