gnome-session not starting on debain 8?

Question

Graphic shells

Good evening!
Please tell me, I install a graphical shell on Debain 8:
1.aptitude install xorg
2. apt-get install gnome
3. gnome-session --------------> and in response "silence"
What am I am I not doing that? tell me how, after such my manipulations, then completely remove everything about gnome (after installing such memory, there are absolutely crumbs left)
Thank you!