A diary which matches the current year will prove to be very useful for you to note down and keep a track on what you are supposed to do and when to do. In that way, you can easily plan your work day by day and it will also be useful for revision to break down chapters into parts before revising.
Flashcards are very helpful if you need to test yourself when reviewing notes or learning new vocabulary words for instance.
 Eraser, Pencils & Sharpener
Though I believe most of us do have these things, they are very useful when you are doing past papers as revision. If you are doing Maths questions, I prefer using a pencil to write because in case of mistakes, I can fix them easily.
 Colored Pens & Highlighters
Pens in different colours or highlighters are very useful if you tend to have the habit to write your own notes or is a visual learner.
I saw an interesting pack of colored pens for sale on ebay. Bought one locally and it was excellent and on ebay, it's cheaper too!
 Flying sheets
Flying sheets have many functions. You can answer questions on itself or write your notes. The reason I always recommend to make use of flying sheets when writing your own notes on flying sheets is because INCASE you missed something important, you can just easily write it on another page and place it wherever it should be
Files are useful to keep your notes. If you have huge amount of personal notes, for instance Economics notes, I recommend those Binder files and if you have few notes, you can make use of flip files
 Revision Guides & Past Papers.
If you think that you are weak in a specific subject, better get a revision guide to help you. Past papers should be readily available for you to start your revision
 Study Lamp
Study lamps for a proper lightning if you study at night.
Bookmarks are helpful to easily get to the part of a subject you need to review or study
 Study Snacks & Water
Always keep a bottle of water beside you when studying as if you are thirsty, you won't have to go into the kitchen and get some water which will not only waste your time but you might end up procrastinating. Study snacks in case you are planning to do a long study session
 Educational Apps
Almost all of us do have a mobile phone. Instead of procrastinating on your phone, make use of it by downloading Educational apps or tools which will contribute into your study. For example, there are Podomoro timers apps to break your revision into different sessions .
Use posters to write your notes and stick them onto the wall. It will be easy for you to review them. STICK IT SOMEWHERE WHERE YOU WILL SEE IT EVERYDAY
A 90cmx90cm whiteboard should be useful to write down deadlines or help you in study like sketching a proper graph.
Hope you liked those suggestions, if you want me to add more, reply down below. Please note that you are NOT forced to have all of these.