For most saltwater and bass applications I use a length of mono or berkley Vanish is as large a size as I think the fish will ignore. No tippet required.
Bass usually rate 8-12 pound test. Saltwater up to 20.

For most of the others I wait until sierratradingpost.com has a sale on Dai-Riki tapered leaders (which can get as low as 79 cents each) and buy a bunch. Then I cut off the end two feet and add appropriate tippet. For bluegill that will be 4-6 pound Vanish, for trout I may use that weight Vanish then add smaller fluro tippet if fishing tiny flies.