Kostakis1985, mastering stretching is probably one of the most difficult areas for the aspiring NY style pizza maker. I've spent many hours pondering the best methods for training, and, I have to admit, there aren't any workarounds that make the process faster or easier.
The only aid that I've been able to think of is to make relatively small dough balls (maybe 14" size) and keep stretching them as far as you possibly can. The final product probably won't be bake-able, but the extremely thin stretch will give you a considerable amount of time with the dough and it will give you an excellent idea of how far you can take it before it begins to tear. Generally speaking, if you can stretch a dough that's meant for 14" to something extreme like 24", then, when the time comes for your regular 16" pies, then you should have no problem.
Great NY or Neo Neapolitan style pizza demands a great oven. Have you picked out an oven yet?