Wyvern 13 and other Hunt 13 + Raid (Hell) + Guild War and Arena + Real-time Arena (RTA)

Content wise, focus on getting good gear and working your way up in the hunts. Once you can do at least hunt 11 consistently, you should have an idea of what kind of gear sets you can put together and on what heroes. That will make other content more accessible, like Automaton Tower, Abyss, and Labyrinth. Give these all a shot, see how far you can get, and figure out what your heroes need to do better (do you need better offense, better heals, better tanking, better debuffing, etc.). There's no one spot to focus on particularly because you really need to do it all, but you need gear, so hunts come first. 

In terms of specific heroes, if you're looking for easy-ish wins in PvP, focus on building up and gearing Basar - he's the most cancerous hero in the meta right now if you can build him right and get the right heroes around him. Keep an eye on Chloe too for Wyvern. I don't personally have her, but I've heard she is very good for Wyvern 13.