Some players may have trouble winning PvP battles, making the job of increase the number of trophies a hard task, so allow me to help you to fix this problem.
First Step: Choose an Crowd Control monster(monster that apply Stun/Freeze/Possession/Stamina Drain/Cooldowns Activated to all enemies), then equip the monster you chose with 3 Speed Runes, because an CC monster's function is to go first to quickly stop the enemies. Choose one that has a good trait, because even if he is slower than the enemy's CC monster, the trait can save you because you will be immune to the effect that the enemy uses to deny( it's not going to happen always, because the monster you chose is immune to freeze and the enemy has stun, for example). An CC monster that can stop the enemies for lots of turns, like Cavenfish, also helps, because your attacker(monster that inflicts lots of damage to the enemies) will have plenty of time to kill the enemies. General Thetys and Timerion are great options too, because almost all monsters are not immune to their immobilize skills.
Step two: Put a monster with TEAM Speed runes in your team. If you follow this step, your CC monster's speed will increase, so the chances of him going first will increase. I recommend using another CC monster, so you can deny the enemies for even more turns.
Step three: Choose an good attacker. VoltaiK is an excellent option, and he is arguably the best attacker to use in defense because of his four Extra turn skills, so he can attack lots of times until his stamina is empty. Using an attacker with CC skills, like Metalhead is also a good choice to deny the enemies for even more turns, while dealing high damage.
For defense, instead of VoltaiK, you can choose another CC monster, or a Tanker(monster that is very hard to kill, that has skills that protect the allies, shields, Damage Return and Evasions, like Ouros)to make the battle last more time, so you can make you attacks without losing many trophies.
Hope this helps.