Hey Nhaok
what desktop environment are you after? It seems you want to launch a graphical desktop like XFCE, JWM, KDE or whatever else. Launching xterm with xinit is like building a stereo inside another stereo.
To test that your X install is ok you might wanna try the
default xinit setup first. Also consider installing xorg-apps they are a useful base IMHO although not 100% necessary. But for testing purposes just do:
sudo pacman -S xorg-twm xorg-xclock xterm
Then backup the .xinitrc in your home directory (just rename it) and call startx from the shell.
This will launch the default /etc/X11/xinit/xinitrc with a minimal graphical environment.
If that succeeds you will have to decide whether or not and if so what kind of
desktop environment you want to install.
As a side note you can manually run any desktop environment by issuing "startx /usr/bin/jwm" or "startx /usr/bin/startlxqt" etc.
Hope that helps for now!