CW31 would be a well rounded choice under $30.
Yes, Soundmagic E30 is good too if you can stretch the budget. However, you should be aware of the average/mediocre isolation due to shallow fits (subjective ears).
Or you can consider Brainwavz M1, good value sound for its budget price. It has decent bass (impactful with Sony hybrid tips), beautiful mids and good highs. From what I read online, it seems that Brainwavz products are available locally in Philippines (Digital Walker?) - check out M1 reviews here and online
http://www.amazon.com/Brainwavz-BWAVZ-M1-M1-In-Ear-Headphones/product-reviews/B004IK2EAW
http://www.blog.adelgabot.com/?p=608 >>> This blogger seems to have purchased Brainwavz M1 locally in Philippines










