New gardener here. I am bringing some order to my garden after many years of neglect. I am now at the planting stage and have finished adding plants to one border. What kind of mulch should I be getting? I have a compost bin but there isn't enough ready yet so need to buy some. Should I get bark chippings? Is it ok to put it down now? Do I spread all over the border or just around the plants? All advice welcome!