Having bought the series myself, I know just how expensive it can be. Having said that, WATCH IT.
Babylon 5 is, imho, one of the greatest sci-fi series ever put on television. While not perfect, but then what is. It was the closest thing you will ever find to a well written novel brought to the screen.
Over the course of the series various characters will overcome their own personal flaws, others will develop their own failings, one character will get everything that he ever wanted and discover just how that can destroy the joy of living. Another character discovers that hate and anger must be set aside if any type of inner peace is to found and finds it more rewarding, though harder, then insulting and scaring those around him.
Concepts of liberty, freedom, and, independence are explored, destroyed, and put back together again.
Sometimes the messages are delivered a bit heavy handed, and the sfx for the first season are a bit sub par. Yet all of it is worth sticking with when the galaxy itself becomes the battleground for a war that has been going on for over millions of years.
What did I like most about the series? Simple, as I stated above, the characters grow and change. In the ST series most of the characters were still the same at the end of their run as they were at the start. In B5 you will see real change.
I don't know if this helped sell you on the series or not. if there is anything specific aboutthe show that you want to know, just ask.