Very much depends on the type of lures that you want to use. I prefer lighter rods so I use a 6g-16g rod and a 10g-35g rod.
The 6g-16g is fairly specialised for saltwater applications so a rod that light probably wouldn't do you as an all rounder.
Many modern plastic or wooden saltwater lures seem to fall in the 15g-22g bracket, so that should give you an idea of what to aim for.
For an all-rounder with an emphasis on bass, I would go for something liek 10g at the lower end and 35g-40g at the upper end, but possibly as much as 60g if you know the rod will handle lures towards te lighter end.
Also remember to think about the action. Go for a fast or medium-fast action rod if you think you'll be fishing surface lures for species like bass. (If you think you're not going to fish surface lures for bass, then think again

)