Most traders I see on here like to list it this way:
They're obviously going to list their Wants either at the beginning or the end of their OP (original post). Then, for the haves:
First, their Primes / FAs (Full Arts) / Maybe LV.Xs and Reprints / Secret Rares
Then, they'll list anything notable that is HGSS-on, like good Holos and other playable cards, and then the T/S/S. This is probably the faster way, since it is easier for people to see what they need in the Modified Format.
or
They'll list their cards by set (plus T/S/S). This is usually the more elaborate way, since more players can check in on what cards you do have and which ones you don't. This method leads to less asking of if they need a certain card.
This is the general way I see lists on the Trading Corner currently, so it would be good for you to use one of these methods. I use the first method myself, since I don't mind checking my stuff. If you don't like checking your supplies often, listing by set is the better idea.
Hope this helped.