visible eventcards or not

If you have all the event cards hidden, there is no reason to auction, since any particular hidden event will have the same value to the player. You might as well just deal one face down to each player and move on. Or if only those who are capable and willing to buy event cards should get them, they should have a fixed price, possibly a price that goes up for each event card bought per player (if a single player can buy more than one).

What is the desired distribution, as well? Is everyone supposed to get one? Only people that can afford it get one?

If everybody isn't supposed to get one, then you could flip however many events face up, everyone bids, then the events are randomized in some way to see which one the winning bidder actually buys. All you could really do is estimate the probabilty you will get the tile you want. This would cause this sort of dynamic - Ah, there's 3 of that particular kind of event, and I need one of the other two. If I sit out this auction, someone might get one of those useless ones randomly, and therefore I might have a better chance if I waited for the next auction. Of course, if I win the first two auctions, then there's a pretty good chance I will get the one I need as well as a bonus event.

Or, if everyone isn't necessarily supposed to get one but have the chance, you could deal out an event to each player, those players would then place the event in front of them, and they could choose whether to make a deal for it w/ another player or to keep it. Everyone would have a CHANCE to keep their action, or otherwise wheel and deal to get the action they want, or the money. This would make the auction a zero-sum game, since all the resources are on the table and will simply change hands. Of course, if three of the same action come up, the players who got that particular action might feel put upon, since their market is saturated.

Finally, if you're are using the auction as a means to get money out of player's hands, you could always use one of my methods and associate a cost with actually playing the card. Or you could decrease the player's income. Or perhaps the money leaves the buying player's control, but turns up in the other player's control as something differently valuable, say favor or some other idea, that is powerful but can only be gained in this way.

That's the end of my decent ideas, but here's a random, off the cuff idea -

How about if you flip all the event tiles up that are going to be played this turn, arrange them into piles based on type, and then instead of buying a event, you buy people OUT of the events? Like, say there are two earthquakes, a hurricane, and two riots. You would be decimated if someone played a riot against you, but would be otherwise ok if the other two were played against you. You know that the most likely player to play a riot on you is Bob. Well, for a price of $4000, you could buy Bob out, therefore negating him from being able to effect any of the events for that round. Let's say three players don't get bought out, and two people choose to riot against Susan and another chooses the hurricane. You would then have another round for the last two tiles. You would then not have to worry about Bob. On the next round, if there are tiles left, buying Bob out would cost $6000 or $8000 or $10000 or whatever for balance sake, so that Bob isn't terribly screwed. This, of course, creates other concerns such as "What if everyone else goes to the next round and there are only two tiles, who gets to play?", but you could figure something out.