The part of the card that requires the combo cards to be equipped will not stack (sp regen when attacking, extra damage with mammonite, and +10 luck). It might if there were a way to wear two of each of the combo cards as well, but since we only have 1-slotted armors and footgears, those cards are impossible to stack, thus you can't double-up on the combo effects.
The other effects (polymorph and finding boxes) probably stack, but I'm not positive.