Well, I would recommend creating one collection with 3 fields.
Field 1 - All options (carrots, apples, dory, lager, wine, juice, apollo13, soyuz13 etc)
Field 2 - All sub categories (vegetables, fruit, fish, alcohol, softdrinks, spaceships etc)
Field 3 - All main categories (food, drinks, spaceships)
Optional: Add a 4th field called uniqueID which will be unique to each item in field 1.
Visualise an excel spreadsheet if you can with the above fields.
Then on your screen, add 3 drop down boxes.
First drop down - Main categories (user can only select one obviously)
Second drop down - Sub categories (user can only select one obviously) [Filter --> only if selected in first drop down]
Third drop down - All options (user can only select one obviously) [Filter --> only if selected in second drop down]
Add a submit button and connect the record to the user.
That should be a good start I think. Everything else you have to have a trial and error approach.