Wireless is half duplex, so you should expect no more than half your link speed to start.
If there are other people on the same access point, you can expect even lower speeds.
If there is higher utilization or other access points on the same channel as your access point, you can expect even lower speed than that.
If your client is on the 2.4ghz band, you can expect more interference and more slowdowns because more devices are on that band that cause contention.