1. Firstly, save your gems, when starting to build your base do not waste your gems to speed up your builders, just wait for them to finish, you should only use your gems to build more builder huts. more builders will make building structures faster later in the game.
2. Do not upgrade your defense buildings like canons, mortars, archer towers when you are leaving the game without a shield as this buildings cannot defend your base while they are being upgraded.
Here's the list of buildings that still work while being upgraded.
Gold, exlixir storages
Army Camps
And here are the list of buildings that would not work while being upgraded:
All defense buildings
Gold mines
Elixir Collectors
Barracks
3. What buildings to protect first, the most important buildings you should protect especially if you have still few walls to cover buildings is your gold and elixir storages. When enemies raid you, you will easily lose loots when these are not protected. And also you town hall of course, losing your town hall will automatically give one star to the enemy.
4. When attacking, always deploy your units near the defenses of the enemy like the canons, mortars, archer towers, destroying their defenses first will make it easier for you to win the battle.
5. And of course if you havent connected your google account to your COC games yet, you should now, this is to back up your account in case your game will be deleted you can still recover it, also you can log in to your coc account on a different device.
6. There's nothing wrong building as much gold mines and elixir collectors, and upgrade them one by one, this is to speed up resources production. You can see how many gold mine or elixir collector you can build in your shop.
*I will keep updating this post once I discover some new techniques
I will share the first COC bot I found for android 