To successfully make a moveset, worthy enough to make a good pvp monsters and for catching ancients, legendaries, and ancients, for sweeper, have priority moves (+1 or +2) Higher priority, higher chance it has to go first.
Have stat reducing attacks and stat increasing moves (Liquid defense, Wishing star, etc) and also carry a move that will not drop a monsters health below 1 (Level off, bright shock) also carry moves that recover health, Also have moves that deal a randomly inflicts a status problem, or specify the status problem, some monsters are yetee,plagubonic,sarcuda,albinus,golemet and qillusion
Such as korrodo,anglare and others, have a move that deals extra damage with a move such as choke off and berserker, you also need to carry stat increasing moves and status inflicting moves, such as Event horizon, lethal blow, Make sure to carry stat reducing and increasing moves to make it harder for your opponent to bring your health down, also have the abilities that decrease a specific stat, perfect body or slow tough/strong some good monsters are korrodo,anglare,chromaul,ugoyle,chlorotops and vydral
Always carry priority moves such as shadow slash, destructive blast, and storm calling. Carry moves that deal damage and recover a decent amount of health, such a lunar shot, and carry moves that increase your evasion and accuracy, recommended monsters are grimarrow, korrodo, vesuverex, orogond, anglare
That can be held is your choice, the ones i recommend is accuracy item and orbs (Light,dragon,water etc) accuracy increase the accuracy by 15% and orbs recover health every turn.
Also, be sure to have good abilities to help your monsters, recommended ones are perfect body, slow tough, slow strong, accuracy master and much more!
Some monsters can be used for tanks,sweepers and walls, some very good ones are golemet,yetee,dimagem and odani, they all have very high stats in everything, besides yetee and golemet in speed, so they will be a butcher/tank.