I've never grown veggies in containers, so I might not be the best person to answer this question, but I HAVE filled plenty of large conatiners - up to 13 gallons - for house plants.

I have tried ~

soil from the garden -- too dense, packs and shrinks, then is impossible to loosen.

purchased potting mix -- very expensive at the outset; nearly all of them are now fortified with fertilizer, so the plant is happy for a while, then needs regular feedings, sort of like an addict. I tried 'tough love' - you used to be addicted to fertilizer, but now you're going to get along without it - the plants died.

purchased soil -- no different than soil from the yard, except that it also cost money.

What do I prefer? I mix purchased potting mix with garden soil. If the container is especially large and you expect to move it when it's full, you can put a layer of packing peanuts in the bottom - just don't use the ones that dissolve in water! (personal note - my cat BooBoo likes to touch those with his tongue to feel them dissolve)

Anticipating another question -- Where do I get the 13 gallon containers? They come from the nursery with young trees in them, so just stay alert to where the trees are being planted, and you should be able to get a few.
Another source for large containers is the car wash - the soap comes in 30 gallon barrels.

Good luck, Dean, and let us know what happens to your container garden.

I'm not a MG or a "student of soil science" but, I have had good results with container gardening the past 20 years.

It seems like I move to a different state every 7 years or so and because of the moves I have to start over my container garden each time. The pots have moved with me but not the soil.

I have always used a mix of local "dirt" with store bought compost and peat moss to start my pots in the new location. I then make my own compost each season and add it to the mix.

I'm coming into my 5th year in my current house and all of the soil from last years pots(24) are in a pile next to my deck. In Nov, I added about 1 yard of home made compost to the pile. In April when I fill the pots again...I'll mix in a couple of bags of Manure from Wal*Mart and some of the partially composted stuff from my compost pile.

I always put the partially composted material on the bottom of the pots. The soil in the pot sinks a bit over the summer when I do this... but I allow for this shrinkage by adding a little mulch to the top of the pot.

So, I recycle the soil each year and just add a little organic material to the mix. I also add a little compost tea to the pots each month.

You can $pend money for the commercial potting mixes...but as far as I'm concerned...dirt is OK if you ammend it a little...and I'm into frugal gardening.