It all depends on what you want out of a rod, if you want huge distances then you need something that will chuck out a couple ounces of lead.
If you want a lure rod for hard plastic lures then i'd go about 10 to 40g
If you want something with a little more finesse and want to experiment with soft plastics but still be able to use hard plastics and small metals for bass, then i'd go for something about 8 to 28g. this will give you more feel at the lower end of your casting ratio.