It looks like your upper tension is too loose. Using "cheap" thread is really a mistake. There can be bumps along the thread, thick and thin areas in your thread which can cause tension problems and breaking problems. Don't ever use hand quilting thread or any thread that says "glaced, glazed or coated". These thread are not meant to go in machines and can gum up your bobbin area and needle. Here is a Home Machine Reference guide that might help you with tension, needle size, etc.
http://www.superiorthreads.com/media..._HOME_9-11.pdf
This really helps me when changing threads or having problems. Needle size, tension and delivery are three things to check.
Ricci