For now, there is not much to say about the equipment, because it is difficult to recognize well-maintained equipment.
Just because a bottle of oxygen is scratched does not mean it’s not good. However, it should have a stamped TÜV date or a date sticker that must not be older than 2.5 years.
It is not uncommon for regulators to look used, as well. I have on the other hand made the experience that new equipment did not work.
Suit and booties as well as regulators should of course be clean and disinfected, which is usually standard conduct.
By the way:
I can only advise not to pee in the borrowed diving suit, since this usually leads to the purchase of the suit.