I regularly work the "Fife Circle" route. Firstly you have to decide whether you want to do the whole circle in a 'oner' so to speak ie out & back on the same train with no stops or if you want to break your journey at various stations enroute.
For the full circle with no break you only need a return to
Rosyth Halt or
Dalgety Bay it does not matter which.
Personally I think it beneficial to get off and see a bit of the country so would suggest alighting at
Aberdour (Castle, beach. old church, doocot, &c),
Dunfermline Town (Palace, Abbey, Abbot's Hoose, Park, &c), &
Dalmeny (right under
"the Bridge - just walk down the path towards the Hawes Pier - lots of pubs, hotels, & ferry to Inchcolm Island).
If breaking your journey then you will need a return to the dearest priced station that you intend to visit - if you are sure that you want to break but are not sure where (ie you want to be flexible due to weather conditions* or just fancy the freedom to alight at will) then buy a ticket to
Glenrothes with Thornton.
Any Questions then feel free to post here or PM me. Enjoy!
*weather condition can be vastly different at the various stations enroute - just like today rain at one stop then sunshine at the next*