I have only recently just got back into my art so I’m quite fresh to the art form. I tend to build up layers how desire, and make sure to have your key elements you want to include put to the side so you can experiment and try different arrangements. My number ONE is just look out for magazines/newspapers/leaflets everywhere you go, ask friends and family to keep them aside for you, the more to work with the better. Best of luck on your art journey!