I'd say second time isn't too harsh. If you don't learn from it the first time, then you're not really paying attention to the game. Not putting down your prizes, not counting your hand before Steven's Advice-ing, forgetting to remove damage counters from opponent when using Milotic's Wonderhit...
They are all absolutely unacceptable, and are all irreversible if play goes on long enough so that pokemon get KO'd and whatnot. Prizes not being put out should be an automatic game loss. The other two should be prize swap first, then a game loss. Prize swap is a good rule to enforce in these types of situations, as is game loss, as they are all huge, and can't be proved to be accidental, as the player could have done it on purpose. Not putting down prizes then Oracling is something a few players did at Nationals, and judges didn't have the guts to even prize swap. Judges need to step up to the plate and lay down the rules, and HARD.
On second thought, don't. My deck could really benefit from that no-prize/Oracle combo, especially when I'm only given a warning. =/
~w00per