How to have custom posts

I am creating a local community site and I want to have similar functionality to freecycle, that is users can offer things to other people for free. So they’d need to be a drop down box to say if the thing was a wanted or an offered item. A title field for the name of the item. Then details of the item. Upload an image of the item and a location field, where people have to pick it up from. Also possibly a contact number field.

How is the best way to do this? Considering I want to be able to use these posts on other areas of the site e.g. in a sidebar showing most recent items offered. I also want to be able to add a minimised version of the form which will sit in the sidebar of certain pages, so the user can add an item whilst on a different page.

I’m new to wordpress!