Silverbeet is the absolute easiest thing to grow, and spinach has to be next. There are several varieties to choose from, the seeds germinate in a heartbeat, (well, between one and two weeks), and you can eat it raw in salads, lightly steamed, or made into the easiest, most impressive,
best-tasting spinach and feta souffle. You can email me for the recipe.
Spinach will happily grow in full sun and semi-shade, in the garden, in pots - in fact anywhere provided the soil is well worked over and fine textured. It's a hungry plant so throw in lots of compost and manure.
One trick is to dig the soil right down to a depth of 30cm, because the tap-root can develop that long. You can sow it right through summer, autumn and again in spring.
If you haven't already, try the New Zealand spinach with the exotic name of Tetragonia expansa. I'd grow it just for its look because it's a really pretty trailing plant with unusual, triangular leaves that look almost like a succulent.
Soak the seeds in hot water for 24 hours and then sow three or four in a raised mounds spaced about 60cm apart. This is a "pick me, pick me" plant so the more you take the more it'll make.