Scroll through everything. Tap any photo to see it bigger. When you find something you want, tap I want this on the card — it's saved the moment you tap, and you'll be asked if you want to add a note.
You can write a note or a guess at what it's worth any time and press Save note or Save. Typing also saves itself after a second, so nothing gets lost either way. Each card tells you where it stands. You can answer for someone else with the little menu, and everyone sees everyone's answers.