first age:
This is the conquest forum so i assume Concuests us played
If you play at a difficulty level where with your skill you can beat the AI to the republic slingshot, do so:
research alpha-writing-code of laws-philosophy.
If you are first to get philo, you get a free tech. Take republic, it is the most expensive tech in AA.
If you can start with writing, decent or good players should be able to do this up to at least emperor. Higher than that you need a good start and some luck.
If you must start with alphabet, it is a little more difficult, but still possible up to emperor.
If you play at a difficulty level where you are not able to do this, you can either choose to go for research at minimum or even none at all, using the money to buy and trade some techs after they are known by multiple civ's.
Or you could go for philosophy without code of laws first and then take a tech that is usefull for you. Trade writing the turn before you get philosophy to have acces to more techs. Basically take the free tech a tech that no AI has so you can trade it away.
Literacy is a tech that the AI is not very likely to research. This can sometimes be a decent choise for you to research therefore. For getting it free from philosophy not really though, usually you can get a more valuable tech. (unless the AI has all valuable techs and lit is the only one you can get that they do not have)
After doing any of the above things, you normally can trade for iron working, horseback ridng and some religious techs.
Then it is time to research construction or currency. Currency is the least researched by the AI of those 2.
I do not agree it depends on your victory type goal. In AA, you just want to get to MA asap. The slingshot is miraculous and if impossible to do it with COL, it is still always better to research philosophy first and get whatever you want for free than to research any other tech instead of philo. (As long as you know you will get it first, so dont trade away writing until you almost have it)