Welcome to FreeBSD; I hope your time using it will be as rewarding as mine has been.
Where to start? Well, I would suggest that extensive reading be your next step. You've already covered several topics, some related, some not.
X (I'm not sure if you have XFree86 or Xorg) is the windowing system, and usually installs with a very basic window manager, called twm, which is not at all eye candy, and not much fun to play with. You can start the X server by issuing 'startx' at the command prompt.
In order to build a GUI desktop environment, you will need to install a window manager and any apps that you wish to use on the desktop. KDE and Gnome are popular Open Source desktop environments, complete with all of the bells and whistles you may (or may not) be looking for. Many people, including myself, prefer a light-weight window manager, and a custom set of apps.
There are many, many window manager for you to chose from.
However, I would take some time to read this
chapter of the handbook and get familiar with the ports collection; it'll save you alot of time in the long run, and is the easiest way to install and maintain software on a FreeBSD system. In the ports collection you will find more applications that you can shake a stick at, and they're organized in categories, ie window managers will be under /usr/ports/x11-wm
Once you have a window manager installed (I use blackbox), then you can create a file in your home dir called .xinitrc. This file will eventually include lines to start all of the applications you want to run when you do 'startx'; an
easy one-liner would be something like:
/usr/X11R6/bin/blackbox
Then, when you issue 'startx' at the command prompt, you will get a graphical session with the blackbox window manager.
To get X to start at boot time, and present you with a GUI login prompt, you'll need to configure your system to use xdm(1), which probably installed with X. Your best resources are the FreeBSD
Handbook, the
FAQ, and the FreeBSD
mailing lists.
Good luck, and welcome, again, to the FreeBSD Community!