Okay, I've read and re-read both the manual and the in-game tutorial. I've boosted my luck to 10 and bought tons of different cards. But I cannot for the life of me figure out how Caravan works. Sometimes I can add a card to a pile, sometimes I can't. Sometimes none of my cards are legal, so I have to skip the round or discard a pile of cards. The enemy always puts another card on one of his piles, and if they're between 20 or 27 he wins, I get that. I just have problems getting any of my piles up to 20 before I'm prohibited from using any more cards. Could someone with an enormous patience, a lot of goodwill and some experience with Caravan explain to me how that game is played?
The short answer is use only 10s, 6s, and Kings. Or just 6s and Kings if you have 15 of each.
Hopefully in your starting hand you'll have 3 tens to put down and at least one King. Put the King on your 10 to make it 20, then either have a 6 in your hand to make 26 or wait for a 6 and work on your other piles. If you only use 6s and Kings then it's pretty obvious what to do, 6+2K = 24.
Either way, King your opponents stack if they get between 21 and 26, but the AI is terribad so Don't really worry about it.
On a side note: Theoretically there should be at least 28 legal copies of each card, right? Four suits and at least 7 'sources' - The 4 casinos, Vault 21, and the traditional red and blue decks. So how come I have been pretty much everywhere and don't have nearly 360+ cards in my available deck?