Do a Fast Castle build.
Note: In feudal age you will need two buildings to advance to the next age, normally these two buildings are something like a stable and a blacksmith. But since you are doing an Fimp build, build a market and blacksmith instead.
There is no actual build order for Fimp, but there are a few things to keep in mind.
Build two towncenters as quickly as possible. Build mills next to farms to minimize walking distance for villagers.
Do your best to make sure that all towncenters are working, don't build military until you are imperial age.
Focus on gathering food and wood, not gold and stone! The 5 villagers you have on gold will provide enough gold to your stockpile by the time you are ready to go to the imperial age.
Get economy upgrades as soon as you are able to get them, this includes mill/lumbercamp/mining camp upgrades, and most importantly wheel barrow in the town center.
You should strive to have approximately 50 villagers by 20 minutes game time, if you don't hit this mark, don't worry.
As you approach the 28-30 minute mark, you will have enough resources to hit the imperial age button, make sure you have built a monastary and a university, they are the alternative to building a castle!
Hit Imperial Age.
----Things to keep in mind before attempting this strategy.----
It is risky, only do it if you know your allies can protect you while you Fimp.
A strong castle age army with armor upgrades is better than a weak imperial age army with no armor upgrades.