Evernote

Free (IAPs) | Needs iOS 11 or later

When starting a project you need an app to get your basic ideas down. Evernote can take notes of all kinds – text, images, voice memos (which it can transcribe) – and you can forward emails to it. It makes it easy to build up information, whether that’s mood boards for a DIY project or details of a work plan. You can also share your notebooks with other people.