HERE for the various PVP rankings and their rewards.
What is the maximum number of allies I can use in PvP? How does fighting other players work?
For every level of your character, you can bring 5 allies to battle (up to the cap of 500). For each of those allies, you can bring 6 of your units to battle. The total attack and defense of your best units determines your stats going into the battle. For any units beyond the maximum amount, only the best ones will be chosen. Please also note that every unit (except those bought with gold) has a casualty rate, and can be lost performing jobs or fighting rivals.
Why is this player able to attack me and win?
Skill points invested in attack and defense provide a behind-the-scenes bonus to your combat resolution. These benefits cannot be seen by either attacker or defender in an effort to add a bit of chance and mystery to player versus player (PvP) combat.
How can I lower an enemy's defense?
If you knock out someone's defense buildings or boost buildings, it will lower their stats until they repair them.
Why did I not win any money after attacking a player?
When you look at another player's profile, the money they have is their total amount. This includes money protected by the vault and money that is unprotected by the vault. Only unprotected money can be robbed from another player.
Why can I attack my allies?
In previous versions of the game, players were unable to attack their allies, or see them on the Rivals List. This changed with the addition of factions to the game. Now allies will show up as rivals and can be attack, but your fellow factions members cannot be. They are safe from attack or robbery.