The Training Grounds opens at castle level 11. It looks a lot like a Weirwood battle but it is a pvp action. When you get into the top 5,000 in rank you will receive blue diamonds every 3 hours and a bigger amount once every 7 days.
Note: The game says these rewards do not accumulate, this is incorrect at this time they do accumulate, the 3 hour ones do, I assume the weekly ones do not.
The higher your rank the more diamonds you receive as rewards.
As mentioned above the Training Grounds is a PVP version of Weirwood, but the strategies are somewhat different. All battles in Training Grounds are auto skills and you cannot change them to manual. The obvious reason for this is it would be unfair for the server to control another player in battle while you had manual control.
Your configuration is where you set up your commanders that the server will use to fight for you when someone else challenges you. You should use your strongest commanders, in a similar formation as you use in Weirwood, tanks in front, damage dealers in the back row.
See below for commander choices. The way you set up is different from Weirwood, Training Grounds is better set up for attack than defense or healing
The idea of Training Grounds is to move up the ranks (lower number). When you first open Training Grounds you are presented with 4 players, in the beginning you only see bot players. These are server generated players and are generally very easy to beat.
Each player will show their name, rank in Training Grounds and their rating. The rating can be misleading, don’t pay much attention to it. The real decisions come when you select a player to battle.
Always select the player to the far left. This is the highest ranked player you can fight and will be the hardest battle, but the idea is to move up as far as you can as fast as you can.
After selecting a player to battle you are shown a formation screen similar to Weirwood but instead of troops on the right side you see other commanders. You will see their quality (colour) and their level.
Just like Weirwood Training Grounds uses the green/red arrow system, and just like Weirwood it is not an indication of a guaranteed win, it just means that particular commander lines up favourably against its opponent based on type. Not level or strength.
You get 5 attempts for free every day. When you first start and are well up in the thousands in rank, it is well worth spending the 250 blue diamonds for another 5 attempts. Do this once daily (the next 5 attempts cost 400 blue diamonds) until you are high enough rank to start earning diamonds, or the battles become difficult to win.
One thing many people miss is the ability to refresh the players you see. If you do not feel you can beat the players presented there is a refresh button that will give you 4 new players to choose from. This button has a 10 second cool down before you can refresh again.
This is where Training Grounds is significantly different from Weirwood since you can control your skills in Weirwood AOE attack commanders are really nice to have. Since the server uses AOE attacks to hit a single enemy they are not as effective in Training Grounds.
Also healing is not a priority, the priority is to do as much damage as possible in the shortest amount of time. So Sansa is not a good choice either.
You want your best tanks in the front line still, but you want heavy damage, single hit attackers in the back row.
Front line: Gorrell, Chris, Robb (Kevin for p2p players)
Back line: Shiela, Arya, Soren
Place Arya always behind Gorrell. Gorrell has an inline attack (the only AOE that actually hits more than one enemy) that stuns the enemy directly in front of him allowing Arya to power up, when she does she has a devastating attack that can often one hit every enemy she attacks.
Sheila has a very high single attack, and an attack buff for your other commanders.
Soren also has a straight line AOE like Gorrell and a very high attack.