Assuming that ethernet and powerline (homeplug) adapters aren't an option for you, there are several things you can do to improve your wireless Steam Link experience.
One of the largest causes of problems on wireless networks is interference. If your PC is trying to send data to your router while your router is sending that data to your Steam Link, they'll interfere and you'll have a really choppy experience.
The strength of the wireless signal is affected by interference from other wireless networks, distance, and walls, floors, metal, and electronic equipment between your wireless router and the Steam Link. Sometimes moving your router to a better location or moving your Steam Link out in front of your TV can help dramatically. Also make sure that your PC and router are in open, well ventilated areas, as their performance will be reduced when they are overheating.
Other applications using the wireless network can interfere with game streaming. If someone is streaming movies or audio, using BitTorrent, or using a Chromecast, try having them stop and see if that improves things.
Some wireless routers have bugs in handling the amount of UDP traffic sent in In-Home Streaming. Please make sure your router has the latest firmware updates to resolve any known issues.
The streaming quality directly affects the amount of bandwidth used for streaming, so reducing the visual quality will help.
You can directly limit the resolution and amount of bandwidth used in the advanced streaming settings. If you want to tune things exactly right for your setup, you can start at 3 Mbit/s and slowly increase the bandwidth until you start getting hitches and then drop it back down. You can do this live while your game is running by bringing up the Steam overlay with the guide button or Shift+Tab and going to the streaming settings panel.
While upgrading your hardware is not guaranteed to improve your experience, upgrading to 802.11 AC wireless is often helpful. NVIDIA has created a list of recommended routers that are also good choices for Steam In-Home Streaming: http://shield.nvidia.com/routers