I'm giggling as I write this because already, you are getting conflicting advice. You will find that this is going to be the norm. Hear us out, then think about it, and do what works best for you.
Now there is some good advice.
Let me tell you a bit about topsoil. Topsoil is that wonderful thin covering of material that covers much of our planet. It is where plants get their nutrients so they can grow and feed us.
Soil consists of clay, silt, sand, sometimes gravel, organic matter, humus, chemicals, a whole community of small critters down to microscopic, (worms, insects, bacteria, molds, yeasts, fungi), water and air.
Nothing you can buy in a bag has all of these essentials of soil. Even if you buy real topsoil that has been stockpiled by the dealer, you will basically be getting sterile soil, because just stockpiling it disrupts the living organisms.
This is why I recommend that you use at least some of your existing soil, and ammend it with other things to lighten up its texture and build its organic content. The organic matter is worm food, microbe food and fungi food. Eventually the critters will reduce oragnic matter to plant food and humus. The humus improves the texture of the soil.
A mulch of plant material retains moisture and at the same time the critters will start working on it.
Also to grow plants, don't forget sunlight. Put your garden in a sunny location.
Enough on that for now. Just let me say that I grew up on a farm. We had plenty of space for a garden, and I still do. Thinking of planting in raised beds or containers is foreign to me. Thinking of planting in any other medium than that left by nature is also foreign. I do heartily believe in nurturing the soil and incorporating lots of organic matter into the soil.
So, perhaps we can say that we live in two different worlds, but the essentials of good soil will remain constant.
Lots of schemes have been hatched to grow garden produce in limited space. You will find proponents of each style of gardening. You will encounter these methods if you do some reading and research.
Applestar gave good advice, do what works for you. The problem is that for the first go around, you don't know what that is. It is going to take several seasons to start getting the idea of what works for you. I believe that those who have given you advice are growing good gardens, and I don't believe for a minute that any of them would give you bogus information. Each has shared what has worked for them. There is a lot of ways to grow things.
Just one note of caution, if you use manure or bagged fertilizer, be careful. A little goes a long ways and you can over do it, then plants won't grow at all in it. What happens is that the solution in the soil becomes denser than the solution in the plant cells and the water moves from the plants to the soil trying to make a balance. Yes, the soil just sucks the water out of the plants and they die. Don't kill your plants with kindness.
Have a great garden.