I single run of cinderblocks is going to be the cheapest durable option.

Cheaper yet is the plastic landscape border bent to hard corners, but its hard to get that deep enough on a new bed. I have tried it myself, and it works in a pinch or where looking good is more important than being stout, but its not a preferred method of mine.

4x4 will get you more bed space per foot (16 sq ft) of edge compared to 5x3 (15 sq ft).

Soil mixes are described in the FAQ. The short story is to search around for the cheapest sources of compost you can find, and start making your own compost too.

If you rush, you could still get in a fall garden, otherwise, you could get your compost and compostables into the bed ASAP and it will have settled in nicely by spring. Save your best compost to top off the bed after getting the rest of the filler in.

Thanks for the suggestions. Do I need to put plastic or something down on the ground over the grass, before I dump the soil in? How many concrete blocks deep do you think it should be....two?

Thanks again,
tms

Don't use plastic, instead try a couple of laryers of overlapping cardboard and/or sections of newspaper over the ground, after "scalping" the grass below with a mower. I'll usually put hte paper down first, then the blocks.

With the 8"x8"x16" cinders, I just use one course. You are ideally looking for at 6-8" of bed with the existing dirt below that, a little deeper when the beds are on pavement or solid rock.

I've made beds work with just a 4" edge, but I did it by piling up the compost thicker in the middle, and I'd been working beds a couple of years before I tried that. First time out I'd stick closer to the program and use at least 8" of bed.

If the garden is for next season, you have time to make lots of compost in a bin, pile, or layers (sometimes called sheet composting or lasagna beds). That way you could save a lot of money for the soil mix.

Lots of info in the Soil, Compost, and Mulch forum on that.

Ray has great advice, as always! My beds are 7 1/4 inches high over clay soil and working well, so 8-inch high cinder blocks should be fine. Have fun.

--Riff.

Here is a link that might be useful: Soil, Compost, and Mulch forum