Let me tell you what ive done for my cosplays that ive been doing since k con 05. I myself have basic sewing skills, but I never have the patience to make things from scratch. What I do is shop at thrift stores and pick up pieces that are similar to the outfit I need. Then, using my basic sewing skills, I modify the pieces to make them perfect. For instance, I was Kabuto one year, yeah? The dark blue top and bottoms were both from the thrift store, and the sash was just a brown scarf. The wig was from party city, as were the glasses, and the shoes were also bought and modified from the thrift store.
that having been said, Im sure it doesnt sound very impressive. but it can actually yield some pretty fantastic results.
http://i9.photobucket.com/albums/a82/Kyumi/Kumori_Con_2006_cosplay_Kabuto_by_K.jpgnot the best picture in the world, but you can get the general idea. (the fangirls wouldn't leave me alone...aiyee! everyone thought i was a boy! xD)
This year for shion, my top is just a white sweater, and im going to remove the sleeves. bam! perfect.
After having sifted through the thread, It seems like everyone has already pointed you in the right direction for your haruhi costume. But for future costumes, you can keep these ideas in mind.
happy cosplaying!