Try and use cards of the same suit, limit your deck to two suits.
Don't bother with queens or jacks, none of the opponents I have met were clever enough to need these cards to defeat.
The best strategy is to hit 26 too fast for them.
Use lots of kings of any suit. The more kings you have the lower the numbers you can use in your deck which makes you more 'accurate'.
Also kings are the best weapon cards. If your opponent is at twenty or so on one of their caravans then slap a king on their highest card and overburden them.
My deck is spades and usually is as follows:
Aces 2
Twos 2
Threes 3
Fours 3
Fives 2
Sixes 6
Sevens 0
Eights 0
Nines 0
Tens 5
Kings 7 (of various suits)
And I win without much effort and without relying on luck.
An alternative is the two suit deck I had before which was as follows:
Hearts:
Sixes 5
Tens 5
Kings 5
Spades:
Sixes 4
Tens 4
Kings 4
Jokers 3
This deck proved to be way to brutal for the computer players to handle and they would often draw a gun after the game and start shooting me. (JK).