if you are going to have limited amount of line here is what is best.
For rivers, get the rio multi-tip or something compariable...SA and such. This will cover all kinds of situation for salmon and steelhead fishing. Full sink for rivers is useless, cause u can't mend full sink lines in moving water, execpt for coho fishing in "frog" or slack water where u can use a clear sink line and doesn't need mending. But even here a floating or sink tip works just fine.
In still water...it all depends on what kind of fishing you do. It's hard to get every situations covered by just one line.
Floating line is probably the #1 line to get and then a sinking line second. all high end floating lines are good. It's more personal preference. Any SA products are good. I presonally use Ultra4. For sinking a slime line or clear line is good to have.
I chironomids fish 95 percents of the time so i don't ever use anything but a floating line that same amount of time with the other 5% of the time using the clear sink. I can basically cover any depth with the floating line by using longer leaders anyways.
If u have the funds you can have a floater, sink tip and a couple full sink in different sink rates. But that will probably happen over time anyways as you find more and more reason to buy more fishing equipment.