There's no cheap way of getting those.
You just buy them at
Disneyland Paris and price is 169€ for Fantasy and 209€ for Dream.
Best case scenario you can find someone who's there at the same time as you, and also has an AP, who can sponsor you.
They give you 10% discount on your AP purchase (per person) and in exchange they get a stamp.
With three stamps the next one is for free.
Photo Pass is just a little card that photographers who are with the characters use to put the photos on they take.
You get the card after the photo and if you want you can purchase the professional photo.
This card is for free, the photo obviously not.
Photo Pass+ is simular to the regular Photo Pass.
Except you pay 49,99€ for the card and you get unlimited access to the professional photos.
With Photo Pass+ you pay for the product and not for the photo.
You can watch the photos online for a year, however the card itself is only available for use for a timeframe of 10 days.