If you really just want a skin-tight look, a material is going to be immensely easier.  If you are dead set on learning to rig conforming clothing, be aware it's about the hardest thing you can approach in Poser - not that you can't learn it, just don't think it's simple.  I encourage you to watch Phil Cooke's video tutorials on rigging in Poser:

http://www.philc.net/tutorialsIndex.htm

Rigging conforming clothing for an existing figure is somewhat simpler, but it relies on many of the same techniques.  You're also going to need to learn how to design and implement Joint Controlled Morphs (JCMs) for areas like the knee; these are present in all of the more advanced character figures, and need to be replicated somehow into any tight-fitting conforming clothing.

http://www.nerd3d.com/modules.php?name=Content&pa=showpage&pid=8
http://www.rbtwhiz.com/rbtwhiz_ERC.html

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