For all relevant A+P stuff, Costanzo hands down. That's the only resource you need for A+P. Plus whatever flash card system you use. For path, I like Goljan's RR since it has tons of pictures. You can really go crazy with the amount of resources out there for path so it's essential to find a quality resource that works for you. For instance, some people say Robbins (big or small) but that's a huge text. It's also pretty densely written so it's hard to read. I preferred the pictures in Goljan with his bullet points. Then when Step 1 comes around, you can use Pathomas as the review resource (<200 pages, very easy to go through if you've done it right).
For imaging studies, there's no one best resource that I recall. It's mostly seeing stuff over and over again in different ways. So you can do practice questions on a QBank that has imaging studies. You can look at radiopedia for classic findings. Or just plain old Google images what some of the common diseases look like on imaging, e.g., water bottle heart, Kerley B lines, etc.