If you're looking to learn, the thing I would say is when figuring out how to use a unit, concentrate on that unit, try it against all sorts of targets in all sorts of combinations and find out what works for you. Then pick another unit. There's nothing wrong with building your collection based on what you want to paint and what you like, though there are some nice looking models that don't perform that well (cough, wyches, cough).
But above all - don't give up on a unit simply because it has a bad game, you may have rolled below average for it, or picked the wrong target, or particularly with the Dark Eldar units, you may have tried to achieve something at the wrong time in the game. Playing the units will teach you more than reading it in a tactica, though that will certainly point you in the right direction.
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Tan? You're joking, I'm a gamer, you're lucky I'm wearing deodorant!
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