What can I grow in a small greenhouse ?

[ZandraJoi]

I am looking some vegetables and tomatoes for growing in greenhouse which are costly here. I am tired with market fruits that are poisonous for humans. I know it is very hard to achieve anything, but just want to give a try for few plants.

Tomatoes, leafy greens, squash & zucchini seem to be easiest to grow.
I understand the need to grow your own. It seems more & more are trying their hand to help cut costs. Plus they will know what goes into their produce.