okay I have three 3* and one 4* CE and I want to know if I should be farming all three of them at once by balancing the bonuses as +4lumber+4stone+4iron
or should I farm them individually on their own quests with +10 on lumber ,+8 on stone and +7 with iron
Depends on whether you want to clear shop or just get certain things from it. Outside that, there is a simple rule - if you can rush any resource, do it instead of farming all at once, because it should be easier to max one of them. You should run once Cave, Grasslands and Jungle (stage 6) with respective buffs and check if they give you more mats than 3 runs on Mountain 6.
Personally, I'd farm the respective resources on their own. Your +10 lumber, +8 stone and +7 is very good for farming in their respective areas. Especially if you do the math, you can possibly get more than 100 for each resource in one go, or if you're extremely lucky, you could get more than 150 (it happened to me once or twice for I think).
Again, these are my thoughts, so do what you think will work out for you!
