The "flashcards" class [1] allows you to easily write nice index cards using LaTeX. I enjoyed using it to write well-typeset cards when studying for exams. You can buy printable perforated index cards for printing [2], but due to price I just used normal A4 paper with 3 cards per page and cut them manually using scissors.

[1] http://ctan.uib.no/macros/latex/contrib/flashcards/flashcard...

[2] https://www.avery.com/products/cards/type/index-cards