Thank you for your reply Keith, I guess things are pretty clear for me then. I'll start of with buying the equipment (what I meant with installation) second-hand, I guess that's okey. I won't buy the entire lot at once, I'll start off slowly
About the straps, belts and sleeves: the conclusion that I've drawn here is that it will be for the best to just buy everything new. I don't mind to, and I don't like taking the risk of something tearing up when I'm doing a workout.
So guys, thanks again for the advice!