You are limited in terms of how much Loot you can get, even when you finish all 3 fights. And being limited on Loot limits how many goods you can produce. The Loot sometimes gets the 4x bonus. When it does and I am ahead on Loot, I build additional goods buildings, up to 9 at a time if I have enough Loot.
If you do run out of Loot, that is not a bad thing. It just means that you didn’t get lucky by getting enough 4x bonuses on Loot. In fact, running out of Loot means that you are running your settlement as efficiently as possible. You should not be accumulating a lot of Loot. You should spend the Loot as quickly as you can to produce goods. It is the goods that you need to finish the settlement, not the Loot. The Loot is just the means needed to produce the goods.
Note that it gets easier with each settlement in terms of getting the 4x bonus. For settlement #1, you have a 5% chance of getting the 4x bonus with each collection but that chance increases by 2% per settlement. For settlement #10, you have a 23% chance to get the 4x bonus each collection, which means that you get more Loot and goods and finish the settlements quicker each time.
For those who play on a computer, I recommend using FoE Helper. It will help with settlements by telling you how many of each good is needed for the remainder of the settlement so that you can plan ahead.
You should also avoid building the Divine Statue and the Water Garden. These are diplomacy buildings that produce Deben, the cultural currency for Egypt. Don’t build them. You are required to build 2 of each to complete quests, so build them and then immediately sell them once the quest is complete.
Unlike Japan or Vikings, you do not need much of the cultural currency to complete the settlement. In Vikings and Japan, you need a lot of the cultural currency (Copper Coins and Koban Coins) to produce goods. But you don’t need Deben to produce goods in Egypt; you need Loot. The only things you need Deben for are Nubian Archers and the Path in the Sand. You should get enough Deben from your residential buildings for those. The only time you will need to produce a lot of Deben is to complete the very last quest but you will need very little before that.