Planting out

My clay soil is improved a bit in parts.
My question is: how much good stuff should I use? I'm wonder whether if you add a lot of good stuff around the plants, once they get to the edge, will they say bgggr that, I'm not going any further?
Is it better to mix compost in with the surrounding soil so that the plants don't get too fussy or grow them in good compost so that they get established before they join the real world?

 

I mix compost with the soil at about a ratio of 50:50 in the planting hole. I find plants are pretty adaptable. They are more bothered about amount of sun/shade and not drying out than the ground conditions, assuming a certain level of hospitality of course. The only plants that fail to send out roots tonthe surrounding area are those that were very pot bound before going in, in my experience.

 

Thanks @ view ahead. I'll definitely bear in mind your advice about pot bound plants