If you are a bit mechanical and on a budget try making one of these or
something similar :

http://www.hydroponicsonline.com/11plan01.htm

what this doesn't show is you should use 12-16 oz plastic picnic cups
to fit inside the pop bottles fill these with some washed gravel,
hydroton ( expanded clay) or even glass marbles, aquarium gravel or
pumice rock works as well, you just need something to support the
plant as it grow and grow it will... so much so the roots will
sometimes clog the drain lines. so watch for signs of wilt. use an
soldiering iron the make the holes in the cups, better than a knife or
punch. picture he http://www.hydroponicsonline.com/images/11.jpg

just germinate new starters in agri rock wool or rubber plugs on a 2-3
week schedule so when you harvest one you can drop another in its
place for a continuous harvest. I am able to grow lettuces/mix for
most months of the year, I tear it down and clean/flush it a couple
times a year.

Leave some to develop full head, others for microgreens, throw some
herbs chervil is good maybe even baby carrots for their tops in there
as well.

For really cool periods in a Greenhouse use an aquarium heater and/or
consider further insulation of your solution tank*. For really cold
periods further make a bubble warp enclosure to protect and still
allow light in

A cheap 10$ shop light will supply enough supplemental light to grow
greens in most places if you use it inside or have such overcast sky
as we do in the PNW.

*good insulated cooler ( with drain) works better than the Rubbermaid
tubs, but they are ~/= 35$ to the Rubber Maid's 5-7$. you can use
building styrofoam insulation to surround the rubber maid bu tyour
back around the cost of an cooler again.

a pretty cool vertical setup:
http://www.hydroponicsonline.com/ima...tical_6_30.jpg