ok where to start....
no lift is 100% complete. it's your job to educate yourself and find out how various components work, and what needs to be changed and why. generally, it goes by money. the cheaper, the less complete. the more expensive, the more complete.
the best bet is to read, learn, comprehend and repeat until you can make your own educated decision. build your own "lift kit" based on what you learn, and what components are needed, and why.
It really depends how detailed you want to get, how well you want the Jeep to drive, and what you're willing to tolerate. Plenty of folks will say they're happy with X or Y setup, even if they're on stock control arms, have low caster, no bumpstops (shocks bottoming out, or major suspension interferences) and a giant t-case drop....in actuality, their setup sucks and could be improved immensely. They'll say they don't have any problems, but the real story is they have never checked to see if they actually have problems. When you don't know the difference or how stuff works, ignorance is bliss. But when you drive a rig that's setup well, and you notice the nuances that make big differences, you'll understand just how bad the incomplete setup really is.
For example, when you lift the Jeep and put bigger tires on it, don't forget about brake & steering upgrades to stop the larger tires (~$200-900). Longer brake lines will likely be necessary. Adjustable control arms will allow you to set axle position (~$900), adjustable track bars will allow you to center the axles under the frame (~$200-400). All this stuff requires some fine tuning work & time to make it all fit together....full bump, full flex, full droop checks, setting axle position, caster, pinion angle, etc.
Now, as for springs - normally 2" or 3" springs will yield 2" or 3" lift, over a stock Jeep...but that also depends on how much weight you're carrying around (bumper, winch, etc). It depends on the spring rate and spring length. This is another factor you have to consider when building your own "kit", or when adding extra weight.
TJ Tech BOOT CAMP: A must-read for new TJ owners/forum members - JeepForum.com
Lift Install & Suspension Lessons Learned
Ultimate Wrangler Build Ups and Swaps thread - Pirate4x4.Com : 4x4 and Off-Road Forum
Suspension Geometry - JeepForum.com
What is a CV shaft and why do I want one? - JeepForum.com
So you want a Tummy Tuck... - JeepForum.com
tj front adjustable track bars for 0-3.5", does yours hit or fit? - JeepForum.com
'rock crawling go-cart' or something - JeepForum.com
Project REDLYNER: Rock Crawler Driven Daily... - JeepForum.com
Music City Flop Project - JeepForum.com
that should keep you busy for a year or so...
and if you're interested in how I set my junk up, read this: Unlimited04's LJ Build - JeepForum.com