Depending on how well the walls come up after using the erasers and sugar soap, I would be inclined to suggest you consider painting the walls. Most marks will be easily removed with cleaner but any marks that have scraped the top layer of paint off will need repainting. It will also improve the look of the room considerably. I would advise using a good quality washable interior acrylic like Dulux Wash & Wear.
If you take a sample of your paint into a Bunnings store they can colour match it for you. Alternatively, you can take some colour cards home with you to test against your wall. These colour cards are more accurate than what will appear on a phone screen. - MitchellMc
Try a magic eraser, otherwise I’ve used adhesive cleaner and solvent (in an aerosol can) to remove marks on walls before. Nail polish remover works too. - prettyliving
Sugar Soap. I see it also comes in wipes now. - Brad
There are some specific cleaning products available in the section at Bunnings, but Sugar Soap is great stuff. - Peggers