Getting a too heavy tripod at first(Manfrotto 055 XPROB). Now I'm going to sell it and get a carbon fibre Gitzo clone(after some research, of course). And no, a 500€+ Gitzo is not an option.
I will never regret my 055PROB, even though I now have a carbon PRO3 version. It was my first decent tripod and I used it for years. I don't understand the fascination with Gitzo, I actually prefer the Manfrotto leg locks.