I had very heavy clay soil when I first turned my ground over with a tiller before 2000. It was so bad I'd have to stop the tiller every 4-5 ft. to clean the tines-----almost gave up. Before I put the first garden in I added truckloads of organic matter in the form of shredded leaves, grass clippings, spillway sand from the Mississippi River and well composted stable waste. Fast forward about 1 year later my soil was MUCH better.
Clay is a bummer, but it can be made better with some work. Almost anything organic you put in it now will only help. It just depends on how much clay you currently have and how much you amend it as to how long it will take for it to become better garden soil.
Right now I have 3 compost piles going in varying stages to be used as things die out and I replant. If you don't already have a pile started, do so and you will enjoy the end result.