To a great extent, it depends on what you need at the time.
I don't think you can put GPP last. This is the most variable of all the 4 you mentioned because the value of a single GPP drops throughout the game. But early GPP are immensely valuable. Suppose you have a city at happy cap, and can stagnate with 2 free citizens ... they can either produce 8 hammers from mines, or 6 GPP (and 6 beakers) running scientists. If it's the first Great Person, it takes 17 turns to get a Great Scientist. You could have gotten 126 hammers in those turns, or a GS. Using settling as a baseline, 126 turns later, you have just as many hammers, but also have 756 base beakers. Over 300 turns, you would have 300 hammers and 1800 beakers, giving 3 hammers and 18 beakers for each GPP. An academy can provide as many as 20,000 beakers throughout a normal speed game (200 beakers per GPP). Of course the GPP for the second GP are only half as valuable, and there is short term cost vs. long term gain to be weighed.
I think a lot of people underestimate the massive value of well used early great people.