Oppressor is nice since you can focus on Ravenous Earth when leveling. You can have a look at Nery’s guide here [1.1.1.2] [Caster] Beginner's/budget vitality RE Oppressor,leveling guide inside,Cabalist version added
You can change the devotions to the ones I have in my Cabalist guide
then you will get the Revenant devotion proc, which will include some player scaling pets.
You will pull the most weight here for starters, but later on when you find more specific gear to the Guardians, you can change the build around 