Hi Kenny and welcome to GoY, could you rephrase your question so it is a little clearer. Are you asking which rocks you should use to create a border or which plants you should put in a rocky border.

The very pretty, free flowering, poached egg plant. Very good for edges and borders and rockeries. Just sow it direct to where you want it to grow - easy peasy. Some thinning out in-situ will be needed, unless you can sow very thinly! I note you are in australia, where the weather is back-to-front from here. If you sow in your late summer or autumn they will come up in your spring. We are heading for spring so you must be heading for autumn. If you want colour for now, then heuchera comes to mind - a low growing autumnal coloured plant that can provide a splash of colour from peach to deep red.

You could just cement some of the bigger rocks together or if its a side you can't see you can build a block wall .

Or, possibly use as a border to keep rocks off of a lawn--or the lawn out of the rocks? If so, the most permanent option would be masonry (reinforced concrete, mortared brick or block, etc.) especially if equipped with a mowing strip. Next down would be metal: stainless steel lasting the longest, ranging down through copper, galvanized steel, to powder-coated steel. Aluminum would be long lasting in soils with a pH of 7.5 or less, but corrodes swiftly in more alkaline soils. Heavy plastic products would be next, but the tops would suffer ultraviolet damage in the dryer areas of Australia. Rot resistant woods--such as cedar, redwood, oak, etc.--might work, but in the hotter areas of Australia might only last a few years. If your lawn is bermudagrass, whatever you use as a barrier needs to be at least 40 cm deep.
Hope that this helps!