[Guide, Camps, Roster] What camps to run, and for how long, often depends on your roster
Unfortunately, Empires is designed around the IAP summons.
This means Uncommon training ( RT02 ) is currently the best balance of Hero XP per hour, Food per Hero XP when leveling, Hero XP per recruit and Food per Hero XP when training.
Currently, kits/ backpacks are one of the most important items in Empires.
Season 2, Province 1 best for kits/ backpacks.
For lower level players, Season 1, Province 5, Stage 8 has very good kits/ backpacks but missing some 4* ingredients.
2.1-8H one of the two best for kits/ backpacks.
(Barry Farmz Here -- Comprehensive data driven farming guide)
Low cost training
Until you unlock Extra low cost training ( RT11 ), Low cost training ( RT04 ) is a great place to store recruits for later Legendary training ( RT20 ). See hoards below.
Extra low cost training
Extra low cost training ( RT11 ) is a great place to store recruits for later Legendary training ( RT20 ), and Uncommon ( RT02 ). See hoards below.
Extra low cost training ( RT11 ), is great for generating Hero XP when you are not in a hurry, short on food or short on kits/ backpacks.
It has the best Hero XP per recruit, and Food per Hero XP when training.
As a general rule, always level with matching colors. ([Links, Links, Links] Discussions about leveling heroes- Updated 2018-Jun-06)
But this is a game, so have fun, if that is your play style ( Leveling: what's best strategy, on-color rainbow or one hero focus?)
Legendary recruit training
Running 2x or 3x Legendary training ( RT20 ) early is very important. Very good source of 4* heroes.
You cannot level heroes you do not have. ( yes, duplicates suck. Yes, camps are designed to get you to spend on IAP for summons ).
Big spenders only need Guaranteed rare ( RT12 ) for hoarding food. Super big spenders only need Extra low cost ( RT11 ) for hoarding recruits.
4* 3.60, 4* 4.70 and 3* 3.50 heroes are good for color stacking.
Even when dead they improved your normal/ matching/ tile damage ( grave damage ).
Color stacking, Empires hidden buff
4* heroes take 26% the food of 5* heroes. So leveling 4* 3.60, and 4* 4.70 heroes, may be your best use of food until you have a decent 4* 3.60 / 4* 4.70 roster. ([Reference, Math] Food costs when Leveling 3* / 4* / 5* heroes [generic food comparison])
Some 5* 2.60, and 5* 3.70, heroes may be more useful than 4* 3.60, and 4* 4.70, heroes. Especially for class quests. (Domitia - my shiny new hero)
Comparing 4* 4.70 to 5* 3.70 can be complicated. ( [Math] 4* 4.70 > 5* 3.70 > 4* 3.60 > 5* 2.60 > 3* 3.50 ( base stats and special skills ) or Comparison of Partially leveled heroes by rarity [More Math] )
Leveling 5* heroes, try to avoid Common ( RT01 ) it uses 2.5x recruits of Extra fast ( RT19 ).
Extra fast training
Too much food?
Leveling heroes with Extra fast ( RT19 ) uses approximately 1.9x food, and 0.73x recruits, of Uncommon ( RT02 ). ([Math] Advanced color training versus Extra Fast)
Extra fast ( RT19 ) is best used on 3* / 4* heroes, but can be used for 5* heroes. ([Discussion] Using item Hoards, Rugged clothes and Adventurer's kits, to level 3* / 4* / 5* heroes)
Advanced House level 9 / 10, can save you world energy depending on your situation. ([Math, Farming] Kit/ backpacks per day versus Advanced House Level 9 [More math, Math Apocalypse])
Hoarding recruits and food
While Elite training ( RT13 ) sounds tempting, even without VIP PASS, you will quickly unlock Legendary training ( RT20 ) which has a much better chance at 4* heroes ( 20% versus 3% to 5% ).
Use Guaranteed rare ( RT12 ) to store food, and recruits, until you unlock Legendary training ( RT20 ). See above hoards.
It is not wrong to use Elite training ( RT13 ), but with merciless RNG, it is not great.
The few people I know who got great 4* heroes from Elite training ( RT13 ), did not have the roster, 3* ascension items, food and Hero XP to level the 4* heroes before they unlocked Legendary training ( RT20 ).
The other trainings
Advanced training ( RT10 ) is very similar to Advanced color training. See color training below.
Recruit training RT05 to RT09 is regular color training.
RT14 to RT18 is advanced color training.
Click for Color training rant
Free version of summons
Camps are not for Hero XP, but free versions of Daily summons ( 150 gems ) and Epic summons ( 300 gems ).
Every time you level a mine, or Watchtower, you get more iron per day.
Every time you level a farm, or Watchtower, you get more food per day.
Every other time you level Advanced house, you get more recruits per day.
Every time you level a training camp, you get less Hero XP per recruit, and less Hero XP per food. But farming the map does not significantly increase your recruits per day and food per day.
Except for Uncommon ( RT02 ), Low cost ( RT04 ) and Extra low cost ( RT11 ) which were probably snuck in when no one was looking.
And Fast ( RT03 ) and Extra fast ( RT19 ) which trade time for food.
The most extreme example of this is color training.
While not the most effective use of your time, and resources, color training can be fun.
Gryphonkit, my wife, uses it all the time.
But it is a poor return on your investment.
Regular color training
The below link has some flaws about food costs when leveling, but still accurate about
Hero XP per hour,
Hero XP per recruit and
Food per Hero XP when training.
Advanced color training
There are a large number of #ideas-feature-requests giving lots of ideas how to fix camps based on the individuals lack of resources in another part of the game.
But from SGG point of view, camps are perfect, just like Atlantis summons.
Note to self
Use desktop computer to rearrange sections for better flow.