I'm not sure what you read that made you so pesimistic. I will tell you that I certainly felt that way to start with. I live in the NC piedmont which stands for a deep vein of red heavy clay soil. White clay is even worse as it indicates that air can't get into the small particles and rust the iron to red. However it is plenty hard and slimy clay like when wet. We have the largest hand thrown pottery community here. Thirty miles south, the soil turns to sand and the interface is the brick capital of the country! I doesn't appear that anything except grass will grow in this soil. However, if ammended heavily with bulk, it does wonderfully as it holds water and nutrients extremely well. We are in the country. I found a cattleman who has cow manure/bedding piled up and mixed after being mucked out of the barns. I bought a dump truck load (I actually bought two and moved it multiple places later) and had a third to a half of it dumped in my ~25' x 35' garden and tilled it in. That could have been between 6 to 10 cu yds of black composted manure. That changed the texture of the soil and it is still there after 6+ years. Gas was much cheaper then and it cost me $60 for delivery and $50 for the manure. Would be much more now for delivery.

I'm fairly new to this forum altho have gardened in various ways for many years but your post brings some questions to mind. I'm curious about the size of your "garden" - will that be large enough for the plants you are planning? I find that quite a small garden and would probably use those 2'x10's and make 3 raised beds which are not so tall. Unless your base is pure bedrock you won't need more than 8" of good soil for most plants. If you loosen the base with a fork it will improve over time. Of course there may be another reason you want to elevate the garden to make it easier to work but you really don't need IMO to have 28" of good soil. If you have any reasonable soil you could fill the tall bed with greens and browns mixed with soil and top it with 8"-10" of good soil, whatever is available. Any worms in the soil will have a feast. If you start a compost bin ASAP you will have some good stuff to topdress your garden in a few months. I've rarely come across bagged soils that are all that good at a low price, and I think it might be a pretty expensive way to garden if you buy that much at high prices. Better to buy some organic fertilizers to supplement until you can get that compost done.

Well Corrine, it actually is compost later on. In 3rd world countries where there's no access to peat moss or vermiculite, they teach this method using only 100% compost. Even if you use the prescribed "Mel's mix", the only thing you end up adding in the future is nothing but compost. After 15 years of my original purchase of Mel's mix(expensive), my garden is now 100% compost. The peat is gone and so it the vermiculite. And perlite is a waste of your money. Folks use perlite instead of vermiculite to save money. Vermiculite is used in this system not only to add fluff, but more importantly to hold moisture. Perlite holds no water. If you doubt that, just look at anything that's got perlite in the mix. It's the stuff that floats to the top. If it's floating, it's not holding...ie, water. If you're trying to save a few bucks just go with 3 bags of 3 cubic feet of commercially available compost. That's enough for a 4X4' filled with 6" of soil and it will only cost you $30. I've got my favorite, but there may be others out there equally as good. But not all compost is created equally.

I used to buy Lambert peat moss based mix which is available at Home Depot. But now I make my own mix. I buy a few of those 5kg block of coconut coir from a local company and get them to sell to me at wholesale price, because they are expensive ordering online. Although a bit pricey, I find coconut coir have superior water retention compared to peat moss. I also buy mushroom compost and horse manure compost. Or I get the horse manure for free from a nursery and compost it myself. I make my own leaves compost with leaves from my neighbor yards, and have worm bins. For the mix, I use my Florida native sandy soil, some peat moss, the coconut coir (one of those 5kg block expand to 2.5 cu.ft.) and the composts. I'm concentrating on making more of my own leaves compost, growing cover crop, making worm casting and getting free horse manure so I don't have to keep buying stuff. My next goal is trying to make some of my own biochar, but not sure if the city will be happy with it. You should look at cover crop and mulching to suppress the weeds, I grow nettle and those things reseeds insanely. I mulch with leaves around their base to prevent them from taking over. Also once the vegetables are already growing, I put down clover seeds, they suppress the other weeds from coming up and does the nitrogen fixing, but you have to watch they don't take over the growing space of the other vegetables. I guess you could cover the raised bed with black plastic and only let the vegetables you're growing go through. My property have lots of weeds before I moved in and my main way to suppress them is covering them with a tarp or some old carpet for a month or two for all the weeds to die, then put raised beds over them. One thing you have to watch out for is trees, or invasive plants or vines, their roots will inevitably go into the raised bed, so I till my beds after each growing season.