Unfortunately TH12 offers almost nothing to a normal player. You need to spend an absurd amount of effort and time upgrading your warden before you become stronger than a TH11. Good news is that giga tesla lvl5 will prevent a lot of 3 stars against you, even with rushed defenses.
Unless you are rushing an account for siege machines, you should stay in TH11 for some time before going to TH12. At the very least, staying in TH11 for 2-3 months to max warden is a good idea.
- Warden lvl20
- Lab lvl9
- Barch lvl8
- Clan castle lvl7
- Army camp lvl9 (260 troop capacity)
- Electro dragons unlocked (at least one barracks lvl13)
- Both spell factory and dark spell factory maxed (lvl5)
- Gold and elixir storages maxed (10mil capacity)
- All 3 DE drills maxed (lvl7)
Its actually a short list, but the first thing in the list will take 2-3 months to complete so it allows you ample time to finish everything else and more. Once you’re done, upgrade to TH12.
Setting up like this allows you to have a short TH12 (1-2 months) and skip ahead to TH13 quickly. You can then slowly grind for a lvl40 warden and lvl20 royal champion in TH13 to achieve your maximum strength.
Read my guide before you go: TH12 guide