What keeps me coming back to and playing through Civ 5 so many times is planning out different paths through the policy trees. Here's some thoughts on that.
I have this whole picture in my head of the timeline and slots available for which policies to pick and when for a science victory. I've never been sure how well I've been able to communicate that in text for each game. Here's an attempt at showing it in a visual timeline presentation.
This is an example for the best line of play I've converged on recently, which is a partial start into Liberty, followed by Piety for the Jesuit Education belief at Reformation, then Rationalism and an ideology. The Poland, Shoshone, Egypt and Babylon games all followed this layout with minor deviations. The turn numbers marked by † are typically gained with a Great Writer, see below.
This timeline shows how I visualize a game's progress through the social policies. Every policy comes in a well-defined slot. My games are never constructed around picking up policies or trees whenever we can get them; it's all precisely planned.
There is no such thing as catapulting through extra policies and trees. The costs escalate so drastically that there's really no way to speed up policies by more than about five turns from the average turn numbers listed there. It costs over 3000 culture to add one more policy to the end of that timeline. Nothing does that. Not the Tradition or Liberty openers, not the Aztecs' kill-culture ability, not the discount of Representation, not French Chateaux, Moais, Brazilwood camps, or anything else. At most a factor such as one of those might come to one additional policy... but why would you do that when Poland gets seven for free.
Notice that there's two top-to-bottom "walls" in the chart, as the Renaissance begins to unlock Rationalism and again for the Modern era when ideologies open up. This is an important principle. You want to push policies to the far side of these "walls" when possible. Every policy slot pushed beyond one of these points accelerates not just that target itself but every policy downstream. That's why the Oracle-Rationalism jump is so important: five policies later, that still has the effect of speeding up the critical level-2 ideology tenet (Universal Suffrage or Workers' Faculties) by an entire policy slot and 10-15 turns! This doesn't happen if the Oracle is used earlier, which puts its policy only on the front side of the Renaissance/Rationalism wall and doesn't affect anything after that.
The row for Poland shows what ends up being the ultimate result of the Solidarity free pick for each era. The actual order varies a bit, as each freebie claims the most urgent policy on the mainline track, then the following regular slots backfill other options. For example, the medieval freebie actually takes a Piety policy sooner (Reformation itself), then the next regular slot goes to Meritocracy instead. The renaissance and industrial freebies each take a Rationalism policy (Secularism and Free Thought) sooner, then the 10th regular policy will backfill into Theocracy instead.
You should always get four Great Writers throughout a game, three naturally spawned plus the Globe Theater. (One more naturally spawned writer takes 400 GPP which is another 40-50 turns, much too long.) They should all be saved until they reach maximum culture value, which is after you have 8 turns of history of industrial age cultured city-states, Sistine Chapel, and a Golden Age. I typically spend all the writers at nearly the same time, but for the chart here spaced them out for readability.
The World's Fair is the one way to add another policy to this list. But that doesn't seem worthwhile, as there's no single policy critical enough to warrant the opportunity cost of Sciences Funding instead. Sciences Funding gains a turn or two on the last scientist and thus the finish date, and there's no single policy that will do that. Plus the Fair costs hammers and takes a while even with AI help.
Sydney Opera House would work for an additional policy, but it comes so late that a science victory should be finished before you would complete that wonder. It might be useful for a desperation grab of Space Procurements or the Rationalism finisher if you otherwise fall short of one of those required components for a spaceship end-game.
Finally, here's another rendering of that same visual timeline. It's the same information oriented vertically, with more space to show the actual policy picked for each slot.
|Policy number||Turn number
|8||110||Mandate of Heaven|
|11||145||Industrial||Free Thought||Commerce opener|
|Ideology early adopter||155||Modern||Freedom/Order||Avant Garde/Hero of the People||Landsknechts|
|Ideology early adopter||155||Civil Society/Skyscrapers|
|12||155||Universal Suffrage/Workers Faculties|
|14||165 (writer)||Freedom/Order||Capitalism/Socialist Realism|
|15||170 (writer)||Atomic||New Deal/Five-Year Plan||Mercantilism|
|Statue of Liberty/Kremlin||170||Space Procurements/Space Pioneers|
|16||180 (writer)||Information||Rationalism||Rationalism finisher||Liberty finisher|