Plundering can sometimes seem like it's a complicated process when really it's quite simple. When you get a victory you get to take the resources from the city you plundered. But when you plunder you won't always get the resources you were hoping to get. Sometimes you get a little of each resource but every time you'll get at least a little gold. Why is that?
The reason for this is because of storage buildings and their protection limits. When you plunder a city you can't collect any amount of resource that is lower than the city's protection limit. Let's say you scout a city and you see that the city has 100,000 gold, 50,00 food, 50,000 wood and 50,000 stone. You decide on an attack because this is a nice haul and the city has a low power level but your troops come back with 100,000 gold and nothing else. What your scouts didn't report back is that the city has 100,000 protection on each resource. If you had sent more scouts you would have seen the resource report that looks something like this.
Gold 100,000 Food 50,000(100,000)
Stone 50,000(100,000) Wood 50,000(100,000)
The numbers in the parenthesis is the protection limit on the said resource. if the city had 110,000 of each resource you would have only received 10,000 of each resource plundered.
Scouting is a helpful way to see if sending your troops out will actually be worth your time. Personally I tend to only really target other players that have 100k power minimum though.