suggesting 24dBi parabolic dish
You can get 24dBi parabolic dish antenna for 2.4GHz for a very cheap price, relatively speaking (of the gain). They look like a BBQ grill except it is curve in a parabolic shape, and has a dipole antenna sticking out. About $60. each, but sometimes you get bulk discount.
You should keep the thin cable, because you cannot attach thick cable to the card without damaging things. Just use as short as possible on the thin cable, and then connect to thick cable, low loss ones (like Times Microwave LMR-400), depending how long a run you need. The cable could cost more than the antenna, if it is a long run, plus the connector. Keep that in mind.
The advantage for a parabolic dish antenna is not only the gain, but the rejection of other signals from other locations not in the direct gain path (straight ahead) is much better than other antenna types. If the dish is too bulky for your installation, then try to use a multi-element yagi design, which is also directional.
The problem with WiFi is not just about the path loss, but there are many other signals on the same channel(s), causing interference, as there are only 11 channels used in North America, and those channels also overlapping each other (mutually exclusive only 1, 6, 11). So you want to have the least interference as possible, and a dish is the better method.
I bought mine from L-Com (actually Hyperlink which got bought out by L-Com) but there are many makers.