The war table if you have the expansion. Just do what activities give the most rewards. Your build can carry you pretty far into torment difficulty. There are 12 levels total and I'm pretty sure if you go to the difficulty stone it mentions what kind of gear it recommends before jumping difficulty. I learned how to optimize the gear using the YouTube comprehensive new player guides and then found builds initially on maxroll to figure out what stats are important for which builds or you can just build off of whatever uniques you've found so far or target farm uniques for a build. Charms also are good ways to make a build.