Hmmm....I read the original post quickly, and thought you wanted a
level line, Jaws.
Anyway, I have a few Headstart lines in 5 and 6wt. They have a bass taper
design (sort of/mostly), and work well for the money. Cortland 444 has long
been a standard line to get, and is less expensive than some of the specialty lines from other manufacturers. If you plan to cast bass bugs, a proper
leader will really help. Don't use a 9 foot trout leader. I tie my own leaders,
but you can buy a 7.5' bass leader from Cortland, Scientific Anglers, etc. You
can/should use a 9' leader for streamers if you're using a floating line.
Throwing big flies is more difficult than little flies, so practice casting. Pay
attention to your rod's position on the backcast: make a proper stop, and
pause for the line to straighten on both the foward and backcast. A good
line will help, but the rest is up to you
.