The correct place to start on deciding what weight of rod / line you need is the size of fly you are going to be casting. that said its a bit late to make that decision now you have a rod. Casting an 8wt line on a 6wt rod is not to be recommended for a beginner. You will want a line to match your rod. (Notice I didn't say 6wt line) Unfortunately it isn't as simple as buying a 6 wt line for your 6wt rod. Is that a double taper (DT) 6, or a weight forward (WF) 6? What I would recommend is talk to your instructor. Most likely he will have several lines ranging from DT 5 to WF 7. Ask if you can try these on your rod when you go for your lesson. He will be able to advise you on which line balances your rod best. Then get that one.
As for leader and tippet. Well the place where it is probably most crucial is in fishing a dry fly on a river. Wrong tippet gives bad presentation which equals no fish. For a dry on a standard light wire hook divide the hook size by 4 and add 1.
Or put another way, hook #12 so (12/4)+1 = 4 so you need a 4x tippet. That is one that will be soft enough to give good presentation while being stiff enough to carry the fly through the cast. A lighter tippet may give a better presentation, but will not be stiff enough to turn the fly over at the end of the cast. It's always a compromise.
The leader, has to transmit the power of the cast to the tippet. as the power turns the line over the power is, for want of a better word, used up. that is why we use tapered fly lines. As the power dissipates that which is left has less work to do. That is not such a thick a line to turn over. when the end of the line turns over if the power reaches a level length of mono it then has to turn that over. What you have is a constantly decreasing amount of power trying to do the same work. Sooner or later the cast will stall. Dropping all the rest of the leader and tippet in a heap. Most of the time you don't want this. Sometimes you do - presenting a dry fly downstream, for example. Sometimes it doesn't matter. There are techniques to make your cast pile lots of loose line at the end. That is what your instructor is for, to help you learn to do things like that, and know when to. First and foremost don't handicap yourself when learning to make a good straight cast. get a tapered leader.
Some will challenge the need for tapered leaders. All I ask of anyone who does that they give me a reasoned explanation, that will stand up to engineering scrutiny, not just anecdotal evidence.
There was a recent discussion on braided loops here. The simplest method I've found is this one
http://www.graysofkilsyth.com/fishing-knot...'s-loop.htmThis may all seem a little complex, but I hold that when trying to do something, even more so when trying to learn, it is always easier if you understand what you are trying to achieve. In this case, how to make the machine of rod and line deliver a fly. I hope it helps.
Cheers,
OT