Clash Of Clans Essentials : Don't Rush You Base

What is Rushing? Increasing the level of your town hall without upgrading one's main defensive buildings (Mortars, Wizard and Archer Towers, Cannons) as much as possible. Walls are important, depending on level, but it’s not a mortal mistake if you don't do each and every wall.

Why not to rush your Town Hall?

1. The Eye Test
2. Offensive Handicap
3. Defensive Penalty

Eye Test
When searching for bases to attack, the first thing many experienced players do is check the Town Hall level. Then they know what to expect. For instance, if you see a TH9, locate X-Bows. If you see a TH8 you know you need to locate 3 Air Defenses. If you see a TH6 you know you only need to locate 1 Air Defense. If you see a TH8 surrounded by lv5 walls with otherwise low level defenses, your confidence rises. Similarly, if you see a TH8 with mostly lv7 walls and some strong defenses, you’re likely going to keep searching for a base to attack.

Offensive Handicap
The Clash of Clans Wikia explains: Matchmaking is based solely on Trophies. However, the loot available to gain is affected by Town Hall level. Players get increased loot for attacking Town Halls of a higher level, and reduced loot for attacking Town Halls of a lower level.

When you're attacking another base, the amount of loot you get is affected by the level of your TH as it pertains to theirs. Rushing your Town Hall does not have anything to do with the level of your troops and subsequently your ability to win attacks against other bases. However: Most people do not max their troops and skimp on defenses. A rushed TH likely corresponds to lower level troops
Though you're matched to bases according to trophies, not relative TH level, the lower TH level you have while still being able to compete, the more loot you'll get overall.

Rushing your base (in conjunction with not upgrading your troops) means you're looking at getting less loot per attack, which means eventually catching up is going to take longer and longer as upgrading costs rise and the loot you receive is handicapped.

Defensive Penalty
Attacking bases with higher level Town Halls is really advantageous. If you're a TH7 and see a TH9 while searching for a base to attack, you'll be able to steal 50% more gold, elixir and dark elixir. If that base rushed and you can take it out, why wouldn't you?

But what if you're the TH9 on defense, not the TH7 on the attack? This means others can take more of your loot. This is the most important reason not to rush: your base might look very juicy to those who leveled up at the right time (The Eye Test) and the loot they'll be able to get will be stellar.

Avoid increasing the level of your town hall without upgrading one's main defensive buildings (Mortar, Wizard, Archer, Cannon) as much as possible. First concentrate on all Mortars, Wizards, Archers and Cannons: ensure they’re all built and fully upgraded to their maximum levels. Ensure all non DE Troops are fully upgraded to their maximum level in the Lab (at least all of the ones you use if you're short on Elixir); all walls are at least the level of your TH up until TH7 (after that it depends a bit); at least one barrack should be upgraded to maximum level.