what do you intend on doing with the cards can have a impact on the paper/card-stock you use. do you plan on using them as a display piece or occasional handling them like cards? playing card stock is designed for heavy use. i would make sure whatever paper you use it passes the bend test (any corner bent to touch any other corner leaves no visible deformation such as creases or dimples to the card after being bent back) and if you want to go a step further get something with a blackout core (so when you hold it to a light you cant see whats on the other side).
you can buy card blanks that meet the criteria for cards that are good to handed
http://www.makeplayingcards.com/design/blank-tarot-cards.html
(i have not used this sight and cannot attest to the quality of there products or customer service)
card blanks are a bit tricky to work with. i do custom magic the gathering full art cards and card alterations on my Epsom inject ns625 using double sided tape and regular paper as a carrier sheet to trick the printer into printing on 300gsm stock without it freaking out/jamming.
you also need some surface prep-products to allow ink to be used on cards without bolting and running
i use a 50/50 mix of golden digital ground and folk art glass and tile medium. you can brush on a base coat wait till it dries and then use a sponge or texture brush to get the texture you want on the cards.clean the brushes after each coat as this mix drys quickly into buggers of goo in the brush (i further mix the "printer gesso" 50/50 with water so i can run it through the air brush and get a very smooth surface with no texture when doing art cards.this is not necessary hand brushing but the liquid wont run through a airbrush unless its watered down)
i also always do a final coat or two of krylon clear matte finish to semi water/oil proof the ink and protect the art from smudging and dirty hands

the left card is printed on medium tooth watercolor paper (3.75x 6.5) and the right is printed on a magic card that was de-inked with acetone then prepped with "printer gesso" and would be a more accurate representation of what you would get with card blanks (minus any texture added with the "printer gesso" as i was to lazy to make a new "textured" blanks and had some full art "smooth" card blanks already done)
im going to make a set of theses some card captor Sukora cards and some final fantasy tipple triad cards as gifts for people so im going to try the card blanks from makeplayingcards.com myself as they are so cheap
side note. it is considered by superstitious people (like people that go to tarot card readings) that buying tarot cards for yourself results in bad luck when using them and any you use should be received as a gift.i am not superstitious but even if i was i wouldn't think this extends to making your own but i could be wrong and big-foot could be real.