You have a lot of tasks to approach your objective.
First, to take the data you can use a json with data of your gallery, like type (image, video, audio), title, description, url of thumb, url of file, etc.. You can use gson to convert the data. To request the thumbs I recommend the Universal Image Loader for Android, it even have some gallery demos.
You need to search about Activity to start another activities and adapters to populate your lists.
I don't know what is your knowledge about Android development so I recommend read Vogella tutorials.
Good luck!