I've really been thinking about creating a deck based on sacred geometry and hermetic philosophy. Maybe a bit of tarot sprinkled in. What is the first thing I should consider?

I don't really have much money but I can do most of the design myself.

I LOVE the idea of sacred geometry playing cards! Have been searching around & nothing really interesting has popped up. Another design I've been pretty keen on that is slightly related & I can't believe nobody's produced them yet are crop circle designs! Not really sure about sacred geometry & tarot crossover though, I don't think I know enough about either to know how they correlate, but would be interested to see if you manage to make the concept work.

As for the production process, I'm about to make a long post about my experience with it. It's been long & arduous & definitely expensive!

I quite involved in the playing card industry, and know quite a bit about making custom decks. For the actual process of making your own deck, check out this article that I wrote on the subject:

How to Create Your Own Deck of Playing Cards

It gives advice about all aspects you need to consider:
● Concept
● Artwork
● Funding
● Production
● Fulfillment

The quantity you're printing will also be an important factor. If you're just doing a small print run, and want a few decks, your best bet is to use a company like Shuffled Ink, which has no MOQ (minimum order quantity), and yet will let you produce a quality product with a linen (embossed) finish. I've personally printed with them and had a good experience.

There is no greater satisfaction than watching a deck you created come to life.