I reckon half of an old set of ear phones, wired to a USB would work
Actually, most earphones have an impedance that is less than 50 ohms, and because of this you will have an impedance mismatch, which you would need a preamp to boost the gain, and even so, you would still have very weak volume as most preamps max out at about 85 db (decibels) of boost, and even at that much gain, you are going to hear lots of self-noise from the electronics that will manifest as 'hiss' and/or 'pop' noise.
Tried this myself a few times. If headphones are the best you can afford, the Apple Earpods ($29 from Apple) (not the wireless ones, but the wired ones) which use a MEMS mic element (as opposed to a traditional mini electret mic element), which is actually pretty good for both voice and music, but mic placement is a huge factor in getting proper sounds without distortion and without sounding thin and/or tinny. You would use the standard headset port on your device provided that it has a TRRS plug for both mic and headphones input. headphones only have TRS input and lack the ability to signal the device inside the 3.5mm jack because unless it is a TRRS plug, the TRS plug will short a connection which tells the device that there is NO mic attached to that plug.
This is an official EIA standard connection now in 2017 as both Android & iOS devices, and most Apple computer computers that have a single 'combo' audio jack will all conform to this wiring scheme in the audio plug and headset devices.
FYI: most dynamic microphones have an impedance between 200 ohms (ribbon mics and cheap dynamic mics) and 600 ohms (Shure SM-57/58, Electro-Voice N/D767a, AKG C400, Shure SM-1, Blue Encore, etc) and piezo pickups have impedance in the range of 1M ohms (1 million) and also need a preamp to correct the impedance mismatch the other way.
Lots of these issues are discussed in the threads found via the link in my signature below, whereby I've given as much technical detail as I can based upon personal experience working a second job, at different times as a DJ/sound engineer as well as in the recording studio in various roles.