If you were digging a hole, and the spade you were using had a shaky handle and a broken blade, you would take a lot longer to dig that hole than a guy with a well-made, new spade. If you were trying to play a guitar and it only had five strings, then you would not get such a great sound out of it as a guy with a new Fender. So when it comes to body building, there is something to be said for using new, efficient equipment. It may cost more than second-hand, and you could buy some cheaper weights, but would the saving justify the use of the poorer equipment?
Badly designed weights can work muscles in the wrong way. The advantage that you gain with better equipment is that, for the same amount of work, they give you far more than basic or poor equipment. There is little point in cutting corners when it comes to training – all that will happen is that you will struggle at some point down the line and you will regret it. At that point you may decide to upgrade your equipment – and all you will have done is delay the spending, incurred some extra and held yourself back.
Instead of this, ask someone who knows you, and who knows training what kind of equipment you should go for. Working with the right equipment is worth the effort and the cost, and will save you money in the long run. There is no point at all in half-measures where training is concerned.