DiabloFans

The flavor of the month? Mine is pistachio. Or maybe vanilla. But for someone else it might be strawberry.

It's the same in D3: everyone has a different preference. Unless you're paragon 1000 and interested to get into the top 100 of the leaderboards, it absolutely doesn't matter; pick your class based on playstyle, the game is incredibly balanced at the moment. There's tons of viable builds, for many classes even multiple different builds that are very strong.

Gear: Depending on which class/build you pick, different items are desirable. It's not like early RoS anymore where it's just "Furnace or go home". For monk, for example, almost every item is useful as it has many different builds that can go GR90+. Similar story for WD.

Gems: Again, depends on your build, but in general there are a few that are never a bad idea: Bane of the Trapped, Bane of the Powerful, Boon of Hoarder (for Nephalem Rifts), Bane of the Stricken (for pushing high GRs). But honestly, in the end it depends on your build; if you play a pet WD you want other gems than playing a thorns crusader.

GRs: A mixture of everything lets you get gear: Nephalem Rifts, GRs, upgrading items in the cube...

As for your profile, the Crusader isn't a bad class as it can go as high as any other class, but it's the least diverse class as it has only one really viable build for high GRs, and that is thorns. If you want to stay on Crusader you should try to get the Invoker set as soon as possible and start collecting ancient items to go for the Legacy of Nightmares Bombardment Crusader. Just check our builds section for invoker builds and "LoN bombardment" builds and you'll find plenty.

Edit: You might just want to check the condensed patch notes for everything that has changed since you played last time. It'd take hours to write up all of this. Plus, honestly, just enjoy the game and don't read up too much, you're just taking away that "discovery" perspective otherwise.