<Um...>
Isn't Gil the currency for FFXI? Thus making Gil the money?
Anywho, I'm going to assume youre a new player. Try doing some repeatable quests. Mandragora mad is a great quest for raising windurst fame and getting some quick gil while you level (there are similar quests in both San d'Oria and Bastok as well). ALWAYS have signet. You collect crystals (which you can sell), but more importantly you collect conquest points. Which you can trade for items from the person who casts Signet on you. Which you can then sell on the AH for usually quite a bit of money.