Generally you should prepare when entering a new Era. Meaning having enough goods, coins, supplies and FPs to take a Strategic step into the next era. Most Eras have different "Milesstones" in the Tech Tree that should be reached as fast as possible to avoid stalling
*.
So if you are prepared properly to enter a new era, then you can aslo delete buildings from the age your are leaving.
*For every age you need to figure out what building of that age are the best. I might very well be that in one age 24H houses are the best choice while in another the 8 Hours houses are to prefer. The same goes for Supply production and military buildings/units. Asking in the forum or searching for similar questions is a good idea. FoE is German based game – Germans love planning
(I know because I live in germany and I am not very good planning).
Overall enterting a new Era it is important to get the Goods building up and running fast – that means that you most explore the Continent map as fast as you can to see what Goods you will be able to produce in the new era – and as soon as you know, start producing thoose.
As already mentioned above by
twomsuk – The game works so that you should delete older buildings for new and better buildings – You could call that a constant change for your city.
I know players that get a bit emotional about their cities and I advice them to take a screen shot and save the image in a FoE Hisotry folder.
In any case their is no problem in deleting old standard buidlings – any building that can be build from the standard buildings can be deleted without much or any consquences, so just delete them - if you should need some e.g stone, then just build it again. When it comes to event buidlings and other special buldings you can go and check how they do and what they give in later ages at the FoE Wiki here:
https://en.wiki.forgeofempires.com/index.php?title=Main_Page
Some special budilings might be worth keeping for several ages becasue they can be upgraded with OneUp or Renovations Kits. Other are worth keeping in the inventory becasue some events quest demands somthing that might seem "difficult" – but then the older buildigns can be usefull for fast solving the Quest and after that just be deleted.
Overall don´t linger with these old buildings if you have new and better buildings to replace them.
OTHER BASICS
– You should nearly always update 1 lane roads when you can – Passive happiness in lower ages are a good happiness support.
– Always try to expand in a square format, till you can´t avoid breaking the square anymore, secondary a rectangle. Low age uneven city space will cost you placement headache in middle-to higher Eras and deny you some building space.
– Always create a surplus of Coins and Supplies for every main collection. Coins should be about double of Supplies. 2 Million Coins – 500K supplies etc.
– Research what GB´s are worth building, several GBs are heavily outdated and not worth the space how tempting they might seem.
– Some very attractive GBs can be build to early on, - E.g Having an Arc is very attractive, but not if you make 50FPs a day and have no high ranking freinds and guildies that are willing to invest heavily in your Arc.
– For rectangular buildings and in paricular if you have many of one type, consider to connect them to to road with the shortest side.
– Avoid having roads running alongside big GB´s like Alactraz – remember any building does only need one road patch to be connected.
Never have roads running on the outside of your city space, it looks great but that way they are only 50% effective. And be carefull when you get to doublelane roads – these are to be kept as sparse as possible – In no Era do they provide as much happiness as 1 lane roads. Having only the roads you need are the key to having more buildings in you city. Quite a few players suffers from "OCD" and make very strict cities, they look great but mostly they are not very efffective in regards to utilizing the available space.
