What to plant

Hi all,
I have a large sloped bed with (I think) sandy soil and full of rocks and stones. (It is subsoil from what the builders seemed to dump in there). It’s very dry. I’m wanting to make a colourful and easy rock garden and wondered what you might suggest planting?
I have some urchins which are growing well and a hebe plant. Not sure how my phlox and newly planted magnolia is doing though (pictures)? I planted in compost with root grow and water a lot every day. Any advice? Picture of bed too.

Thanks in advance

 

Hello Slouise, Have a Google for Cistus, Helianthemum, Prostrate Rosemary, Lavenders, Artemisia, Thyme, Salvias...that will give you something to be going on with