OS X is compatible with a select few wifi chips, so you will most likely have to buy a new wifi adapter or WiFi USB dongle. Most of them are fairly inexpensive though.
Some motherboards include wifi chips; however, for OS X | macOS compatibility you will need a PCI wifi card, these cards work without any additional drivers.
1 Rosewill WiFi Adapter / Wireless Adapter / PCI-E Network Card, 802.11AC Dual Band AC1300 PCI Express Network Adapter
If you have Snow Leopard, you will most likely have to purchase a discontinued WiFi card. Check the OSX86 wiki for details.
It is also possible to build your own wireless adapter out of a real apple airport card; see this guide. Self-build adapters are often the most reliable and cost-effective.
Nearly all laptops ship with wireless cards that must be replaced to get WiFi on OS X. Laptops use Mini-PCIe cards and Half Mini-PCIe cards. Make sure you know which type your laptop uses.
7 Half Mini-PCIe
Of course, if you don’t want to mess with PCI cards, you can always use a USB wireless adapter. They will generally be slower than PCI cards.
D-Link DWA-131 This card will work with Realtek’s drivers. You will have to start them at boot, so your wireless will load slightly more slowly. It works for 10.6-10.8 and should also work on 10.9. TP-LINK TL-WN727N The wn727n requires a patched kext which has been tested on 10.6-10.8 and it should also work on 10.9. The kext should load faster than Realtek’s driver; however, it is more likely to cause compatibility issues. TP-LINK TL-WN727N As with the D-Link, you’ll need a driver for this card. It is designed to work on 10.4-10.8 and should work on 10.9.