A big crappie is going to be a handfull on that 3wt, just a heads-up! We're talking about the same species that I have hooked on my 5wt and been towed 20' or more in my kayak. My opinion on fly selection seems to be different from most folks, I say skip the small dainty stuff. I see folks saying they use nymphs and #10 wet flies, and I think they will catch you fish, but I like to target the bigger crappies. I throw mostly streamers in the 2-2.5" range, but up to nearly 4" at times. Big crappies are fish eaters, so I throw baitfish imitations. White buggers would be a good choice, white zonkers, Clouser's, and even EP style streamers will work well. I almost always start with white or another bright color, go subtle if I need to do so. The biggest one I got this year so far was on an EP shad pattern pushing 4" long, the crappie was 15 1/4". Good luck!