I have 3 barlows. the 1.25" 2X and 3X cost $10 US each on e-bay. Not top of the line but they work fine for me.
Zoom? I have a Celestron 8-24 and would recommend it to anyone. Not a top of the line eyepiece. Comparable to a Plossl in its optical performance which I consider quite satisfactory.
Others will offer their advice but if you want more on what I have just let me know.
This is a little out of date but still good information. This is what lead me to buy the Celestron.
zoom eyepiece review
http://www.chuckhawks.com/comparison_zoom_eyepieces.htm