As your buyer's agent, I would recommend that you offer $5,000 - $10,000 in earnest money. Earnest money is highly overrated. Yes it shows the seller that you're serious, and have some funding. But there are so many legitimate ways to exit the contract and retain that earnest money. As your buyer's agent I like to keep the earnest money as low as possible. The potential to lose that money is slim, as long as you follow the terms and conditions of the contract, but I want it to be small enough that if you HAD to breach the contract, the amount wouldn't be a devastating loss for you.
Now, as the Seller's agent, I want to see a more painful amount on the line. I'd like to see a minimum of $30,000, and would much prefer $40,000... but would settle for some amount in between $10,000 and $30,000 if necessary.... Again, since earnest money is very "returnable" within the terms of the contract... I simply like to see enough money on the line, that the buyer won't wantonly walk away from the deal if they should find a different home they like better than ours, selling for substantially less.