RPi source

sudo apt-get install --no-install-recommends build-essential git bc bison flex libssl-dev python2
sudo wget https://raw.githubusercontent.com/RPi-Distro/rpi-source/master/rpi-source -O /usr/local/bin/rpi-source && sudo chmod +x /usr/local/bin/rpi-source && /usr/local/bin/rpi-source -q --tag-update
rpi-source

RTL8188EU drivers

mkdir -p ~/src/drivers
cd ~/src/drivers/
git clone https://github.com/lwfinger/rtl8188eu.git
cd ~/src/drivers/rtl8188eu
sudo make all
sudo make install
iwconfig ##check that it installed

Update wifi settings in /etc/wpa_supplicant/wpa_supplicant.conf

add to /etc/dhcpcd.conf:

interface wlan0
env ifwireless=1
env wpa_supplicant_driver=nl80211,wext

sudo reboot

to update/rebuild driver

cd ~/src/drivers/rtl8188eu
git pull # Run this if you have Internet access even though your Wi-Fi is down
make all
sudo make install