Wow I don't even REMEMBER half of the stupid things I've done here..
With my first character
-I put every point into either STR or HP, and didn't even realize there were specific JOBS you could become.
-I stayed on Maple Island until my lvl20's.
-Back in the day when super beginners stayed on Maple Island, they would drop mesos in the amount of 100, which looked like money, therefore I assumed it was NX Cash. (and I would beg them for said NX Cash every time they dropped it to tease me)
On my first two accounts, I had random characters in Bera, most of which had at least five Sky Snowboards each. I remember a little over a year ago, the account info somehow popped in my head and I looked in their inventories and DROPPED all the items because I thought they were useless. (I was still such a brilliant noob)
I definitely got scammed by the Skin Care trick. Don't remember what I lost.
I was looting a hacker and picked up Ilbies, only to be asked by said hacker if he could have them, and (of course without knowing their worth) I gave them back.
I'm sure theres more. If I knew what I was doing way back then, I'd probly have hundreds of millions of mesos... :P