When it comes to playing cards, there is a never ending variety to choose from. I will go over the main types of plastic playing cards commonly used to try and give you an idea of what they are like, so you can decide what best fits your need.
Plastic Playing Cards
These are 100% plastic playing cards, they are washable so you can keep them clean. Plastic cards are the top types of playing cards.
Copag - One of the best for the money of the plastic cards Copags are manufactured in Brazil. They are lighter than some other plastic cards, but hold up very well even over extended use. Copags are very flexible so they hold their shape well and have a bit of a textured feel so they are not to slick. Copags are in the middle of the plastic card pack as far as price goes and are a very good deal for their price normally around $15 for a 2 deck set.
Royals - At the lower end of the plastic card chain are Royals. These cards tend to have a very glossy look, and deep colors. They are not as textured as the copag or Kem cards making them very smooth and slippery. Over time the colors on the Royals will start to fade and then feel changes as they become a little more sticky. For extended use Royals simply do not hold up as well as other plastic cards. If you were to only use these cards say once a month or less they would probably last you a year or two. Royals also tend to be the least expensive of the plastic cards typically running about $4 a deck.
Kem - Kem are the cream of the crop of plastic playing cards. They will last about twice as long as any other as long as you take care of them. Kems are about the same thickness of a copag, but are a bit stiffer. The manufacture date for the deck will be printed on the Ace of Spades. If you take care of a deck of Kems they can last you a very long time. Being the best also means costing more, a 2 deck set of Kems is going to run you around $22.00.
A-Plus - A plus cards fall in between Royals and Copags. They are a very glossy card, and are very thick. They are also a bit slippery but not as much as royals. Overall they are a nice card that will run you around $8 per deck.
Gemaco - These are very nice playing cards, they are more smooth and slippery than Kems, but are very thin and flexible. They retain their color well, these cards seem much like a smoother more flexible Kem. As far as pricing they are close to Kems and will run you about $20 for a 2 deck set.
You can find a lot of good deals online for plastic playing cards, in paticular on Ebay, where you can often find auctions for Vintage Kem cards and low priced sets of Royals.