Guys i know that in this field 20€ or 20$ are nothing but i think that for the first project is better to be in "trouble". If you have all the expensive equipment you can't learn how to fix a problem, someone else has thought of it before you.
The important is that when you see the final result, you know how to improve the system if you want to fix one problem and how to act if you want to fix another problem.
For example, in this way i can learn how to build a spatial filter to decrease the divergence etc etc...
Thanks for the advice kecked and swamidog.