Hi Trout master, your friend is talking sh1te
. In a lot of situations a floating line is all you need, i rarely use any other densities even though i carry them around with me alright
In cold weather or very bright sunny conditions the fish will probably be lying deeper, then perhaps a sinking line of some sort(there are many with different sink rates etc) will keep your flys in the feeding zone for longer.
I wont advise on rods but im sure plenty others here will, but a few things to think about are
Whats your budget?
What do you intend to mostly fish for, stocked rainbows, wild brownies, seatrout, salmon?
Mostly rivers, loughs or fisheries?
Feel free to ask as many questions as you like, we were all beginners at sometime and all still learning