I make my own knotted leaders. They have a formula for making each size. As I loose the tippet I just tie on the same size as the last piece. You will need to learn to tie a Blood knot. I have a blood knot tying tool that makes this easy. I bought it from Orvis. You will loose some as you switch flies so you will need to add some to your leader. If you don't want to add tippet to your leader you will need new leaders. A blood knot looks hard but it is very easy knot to tie with a tool. Here is the tool that I have, Blood Knot
There are actually no hard and fast rules with regard to tippet/leader. What I mean by that, is that you need a combination that will turn over your fly, especially on a longer cast, and also provide stealthiness at the fly end, compared to the thicker fly line. There are several ways to go about it. I find I am much more precise when fishing small flies for picky trout. For bass, walleyes, pike just think of all the fish that hit a big lure attached to wire leaders, or heavier mono. So what I do as a general approach is use a straight length of 3' (approx) heavy mono as a leader, say 30lb on an 8wt line, then blood knot or double uni to 3 feet of 15lb mono, and tie a perfection loop on the end. I then will use 8 lb fluoro or mono as a tippet say another 2-3 feet, one end also has a perfection loop, so I can attach the 8lb tippet to the end the the 15lb leader via a loop to loop connection. Changing (lengthening) tippet is now easy as you simply un-loop the shortened section of 8lb and add another length of tippet via the loop system. I attach my flies to tippet using Lefty's non slip loop knot. Most of my fly fishing buddies use a similar system. This also provides an easy and fast way to loop on a section of heavy fluoro if some pike start showing up. Keep in mind as stated that for finicky trout I will use a more standard approach with blood knots or double surgeons knots to tie a long thin leader/tippet. There is a somewhat famous guide around here that uses a straight section of 8lb for all his smallie fishing and he and his clients do very well, so do what works for you.
If you are dabbling, then just buy a 9 foot tapered bass leader. After you cut off a couple feet changing flies, then tie on some 6-8 pound mono with a double surgeon's knot. Keep it simple at first.
Trying to tie blood knots in a canoe, in the wind, with cold fingers... You'll want to throw the whole setup in the lake. Save that for after you have a lot of practice. But it is a good skill to have.
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