This is a short video of a PvP match showing a very basic and easy set up to practice PvP.
16 Grandmasters (Level 18+)
Max all resists
Last two points into damage when above lvl 18.
Rush (Do not sprint) the enemy gaining the initiative and leaving the opponent no time to set up his units. Once near their units go invisible to walk through them and spread your units through all their formations (Preferably where their light units and archers are). Make sure you select and turn on attack move also. Once in the middle of their formations unhide. Your units will spread damage across all of their units instead of standing in line to attack. Now use self heal as needed. Do not bother wasting mana on the resist buff as Grandmasters will have a high resist already.
Notes: You can use invisible to get past their intercepting units. Also, if you want to risk it you can bring a dragon to back you up but be careful as they die fast in PvP unlike NPC sieging. Make sure you bring wardens and Treants to loot
(Don't forget to select 1080P)