Where to buy a cheap domain? Avoid facebook ban??

Hello,
I want to post my aff link on my facebook wall but I do not know where I can buy a cheap .com/.net/.de/.org domain..Any ideas or coupons?
And will my account get banned if I post my link without a domain? Is my account safe when I use a domain?

Sorry for my very bad english...:x

get chrome browser
add honey plugin
go to godaddy
plugin searches 25 latest cupon codes and uses the best one.
click buy

just tried
0.90 eur .com