Make sure you have around 40.000 – 50.000 troops of one kind of Tier1. Then, you need around 70.000 troops Tier3.
Use battle runes if you have any, for some defense/attack boost.
Use your highest level hero.
First thing to do is to look around your city for level 7-10 goblin camps.
You’ve found your first goblin camp. Attack it, use 70-80k Tier3 units and 30-20k Tier1 units.
After the camp was attacked, bookmark it, using the bird icon or whatever you like. Delete other bookmarks marked with that specific icon that are not goblin camps.
Time to attack a second goblin camp. Select the camp, select your hero and if you notice, the same amount of Tier1 troops are already selected and ready for departure. All you need to do is to select the same amount of Tier3 troops, usually you just slide the bar to maximum (so it’s just one click).
Attack and bookmark around 9-10 goblin camps and attack them whenever you have time.
This way, you don’t have to waste time looking on the map for camps.
Also, this is the best troop losing ratio as only the Tier1 troops will get killed, you don’t waste any Tier3 troops.
You can farm/kill goblins for the events or for the third city runes.