Setting up a new garden

Setting up a new garden

We just bought our first house and I'm excited to start working on our back yard setting up a play area plus garden. My in laws came over and helped us prettify our front yard and discovered that no one has ever worked with the soil since the house was built in '96 so it's a combination of soil and drywall and all the crap that they used to build the houses that they mixed up and spread out. Obviously I don't want my plants growing in this stuff so I was wondering what my options are for planting in my back yard that doesn't involve digging up everything and buying a ton of top soil which I can't afford! I've heard about raised beds but I know nothing about them and I'd be worried that the roots of the plants might still go down into the NastySoil. What are my options?
Free Marigold Seeds

Free Marigold Seeds

Plant id

Plant id

Bottle brush tree

Bottle brush tree

Pampass Grass

Pampass Grass

pole bean contraption

pole bean contraption

my pumpkin patch

my pumpkin patch