Don't waste your rubies on useless things

 Many new and inexperienced players tend to spend their rubies on useless buildings, decorations and temporary bonuses (i.e. overseer). Even if you buy small amounts of rubies from time to time (but do not consider yourself as a "ruby whale") you should know the best practice where and how to smart use of your rubies. However, when you are a higher level player, and have also higher level NPC in all kingdoms (some might me maxed) that gives you rubies as a loot, you may consider buying "The Overseer" (in some cases there is a sale for 156 rubies only).

Spend your rubies smartly

There are few building in the game that cost rubies to buy or upgrade and are very important for your game play.

1. Bakery — The most important ruby building in the game. No other building has such a big influence on the way you play the game (!) As the bakery reduce the food consumption of soldiers (in any castle/op it exists) up to 40% (when maxed) it will allow you to hold more soldiers in any castle/outpost hence you can launch stronger attacks. Your goal is to have a bakery in every castle/op and also to have it maxed (!)
2. Stables — The stables are used to speed up the movement of your army, This will affect every attack you make (on RBC or PvP castles, stables level 3 is a must, and will save you thousands of "wasted hours" if you play without that. 
3. Watch tower — A higher level watch tower will give you earlier detect time of incoming attacks, hence giving your alliance members enough time to send support. This is very important in wars, since most of the time you need support against strong attacks. Experienced alliances, when are in war, are seeking to non-WT players (or ones with low level) to start with because the detect time is short, and others can not support just because they do not have enough time.  
4. Fire Station — When you are in a war (and yes, this is a war game...) resulting is fires. A lot of fires sometimes. To reduce fires after an attack (when you have been defeated) you need a fire station. In higher level you will have 1 or more "fire castellans". In addition with a level 4 fire station, you will not get burned at all even if you lose (unless the attacker used a special "fire commander" in this case you will burn in a very minor way).
5. Castle Moat — Better moat will help you to be stronger in defense. This is one of the necessary ruby upgrades before everything else.

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