TF2 trading help (sorry for being such a n00b)

506 hours of Team Fortress 2 and I still have no clue how to do a profitable trade -__-

Selling weapons and buying craft hats takes too much time and there's not much profit. I also buy and sell trading cards as well but it's hard to find people willing to sell good cards (e.g. NO GARRY'S MOD).

So i'm thinking of moving on to other stuff but I want to make a smart investment (I obviously don't wan't to buy tons of stuff that most people aren't looking for).

I have about 24 refined at the moment and I would like some legit advice (NO TROLLING PLZ ;__; ) on what to spend it on, which servers to go to and how to quickly sell those items for a good price.

Thanks for your help!!