Audio-Technica ATH-M30x Professional Headphones - ~69USD
Relatively low impedance at 47 ohms, so will be easier to drive using a portable device or integrated headphone jack on your computer. And they're closed.
Sennheiser HD201 Lightweight Over-Ear Binaural Headphones - ~20USD
Cheaper, than the Audio-Technica's, but don't let the cost fool you. Also only 24 ohms impedance, very easy to drive without an amp on a computer or portable music player. Open, but you'll appreciate open-acoustic cans and I can guarantee that these cans compete with more expensive ones 40USD+
Panasonic RP-HTF600-S Stereo Over-ear Headphones - ~35USD
Only 56 ohms impedance, so fairly easy to drive.
Also of these cans terminate in a 3.5mm headphone jack, so it will connect to mostly any portable device or computer with no adapters or anything
And just remember as a general rule of thumb, the lower the impedance, the easier is it to drive, or the less need for an amplifier.