To get all needed information for compiling and installing on Debian, you can go to http://packages.debian.org/unstable/source/gambas2.

First of all, don't forget to install these packages :

$ apt-get install build-essential g++ automake autoconf bzip2 debhelper dpatch firebird2.0-dev
 gettext kdelibs4-dev libbz2-dev libcurl3-dev libgtk2.0-dev libjpeg62-dev
 libmysqlclient15-dev libpcre3-dev libpng12-dev libpoppler-dev libpq-dev
 libqt3-compat-headers libqt3-mt-dev librsvg2-dev libsdl-gfx1.2-dev libsdl-image1.2-dev
 libsdl-mixer1.2-dev libsdl-sound1.2-dev libsdl1.2-dev libsqlite0-dev libsqlite3-dev
 libssl-dev libxml2-dev libxtst-dev mesa-common-dev unixodbc-dev zlib1g-dev libffi-dev

Then, download the source codes of Gambas and extract them into your home. Going into this directory and run the script :

$ ./reconf-all

Once this script is finished, you can run the common commands to compile and install a program under GNU/Linux :

$ ./configure
$ make
$ su
$ make install

Now, Gambas is compiled and installed on your Debian :) .

If you want, you can make a shortcut in your menus to avoid to run Gambas into a console.