Hi Ionianc, I find that gypsophila grows happily in compost over soil and would plant it with other flowers.
In the UK there are now huge numbers of no dig flower growers and I never heard a comment about the beds being too rich for flowers of any particular kind. Adding compost is not akin to adding lots of fertiliser.
Plus the amounts of compost used are no more than were used in traditional horticulture, before fertilisers were invented. It’s more visible in no dig so that is perhaps why people think you need a lot. The initial dose can be high, to suppress weeds and save time as much as anything. So few weeds, so easy to grow.
See the adjacent post ‘Shock horror’!
