If you do not want to implement a full ERP type system. You can effectively manage inventory with a KanBan card system. The fundanmentals of this include establishing inventory levels, reorder points, and spreadsheet inventory tracking. You will need to isolate your inventory below the re-order point. I find physically bundling your re-order point inventory around your "KanBan card" as the most effective means of ensuring the system does not break down. On your inventory bin you can have a card that will track each transaction (adds or deletions) to keep tracability on inventory. This takes discipline by your staff, but it works really well.