As long as your spouse is a U.S. citizen, you can gift her as much as you want each year without having to pay any gift taxes because the annual gift tax exclusion limits don't apply to gifts between spouses. Even better, you won't have to file a gift tax return for gifts made to your spouse. These include gifts to same-sex spouses as long as the couple was married in a state that recognizes same-sex marriage.
If your spouse isn't a U.S. citizen, the amount you can gift is not unlimited, but the annual limits are very high. As of 2015, you can gift your non-citizen spouse up to $147,000 before any of the gift is considered taxable. This limit counts for both cash and the fair market value of the property you gift. If you go over that limit, you will have to file a gift tax return, using Form 709. However, you must still use up your $5.43 million lifetime exemption before you owe any gift taxes. For example, say you gave your non-citizen spouse $177,000 in 2015. The first $147,000 is tax-free because of your annual exclusion. You then use up $30,000 of your lifetime exclusion, which reduces your remaining lifetime exclusion to $5.13 million.