Even though goblins can't give you 100% 3 stars still its a favorite troop for most of the clashers who love farming. If you love farming lots of loot and don't want to spend half million elixir on troops then this mass goblin strategy works perfectly for you. Since the training cost of goblins are low you will always form 10 times more loot than what spent on training cost.
Troops combination
This differs as per the league, the bases you select, the resource you are farming.
1. If you are in a league where you can find more dead bases (Gold league, Crystel league) then just use full camp space of goblins. Even you don't need any spells if you don't consider about losing trophies.
2. If you are in league with more active bases and consider not losing trophies get a jump spell (Townhall 9), heal spell and rage with some giants.
Strategy
If you like to go with the first category all you need to do is just find dead bases with resource collectors outside the walls. You can easily find these types of dead bases in gold leagues and crystal leagues. If you found one just do start attacking like in this video.
If you prefer the second category that you don't want to lose your trophies you need some spells and troops like giants to distract splash damaging defenses. And the main goal is to take down the enemies town hall. So that you can easily earn a star and get centralized resources buildings like dark elixir storage. This strategy is called as goblin knife and it mostly used for forming dark elixir.
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