"We're saving money each month."
Translation:Nous économisons de l'argent chaque mois.
Following Thierry's above examples, and please someone correct my response if i am missing something but, my understanding is that you use "d'argent" after assez, besoin, or beaucoup because so far we have learned that "de" (and never "des" or "du") follows those words. But if you are referring to some money where there isn't the rule about "de" then you would say "de l'argent".
It is not true that you never use "des" or "du" after adverbs of quantity (although it is not common).
If the original quantity is specific, then it can happen:
- a lot of luck => beaucoup de chance
- a lot of the luck => beaucoup de la chance
- a lot of money => beaucoup d'argent
- a lot of the money => beaucoup de l'argent
- a lot of honey => beaucoup de miel
- a lot of the honey => beaucoup du miel
- a lot of bees => beaucoup d'abeilles
- a lot of the bees => beaucoup des abeilles (de+les=des)