Re: Which lines?
Now thats a question that torments us all! I gave up trying to limit myself, bought a cassette reel and load up my Willy J chest pack - ha ha!
Ok, if I had to limit myself to three - I concur, a floating line is a must. Lengthen the leader, slow the retrieve, using a weighted pattern and I'll use my floating line to fish depths up to 25'. I use a Rio Gold in the flow and a Monic clear floater on the still.
My next most fished line would probably be a clear intermediate. Its a pretty versatile line and I use it on stillwater, on the flows, and in tidal estuaries. I use the SA Stillwater, but had a Rio Aqualux which shot very nicely.
I like a type 3 full sink to get down and dirty. Using the countdown method and with a little patience, I can use it to fish virtually any depth (within reason).
Hope this helps a little.