Good day adventure!
Auto equip of skills is the generic/standard set by the game for your character. It is best way to set it yourself do trial and error, find the skills/combos that fits you.
I do it by setting some skills only for pvp, then another one for world boss/boss rush lastly another set of skills for farming mobs fast. Good hunting!
I pick my own, and trial & error works pretty well. Easiest way I can find is to check how many potions you use farming for, say, one hour with your standard skill equips, then change one or two skills and farm again for the same amount of time in the same area and see if you use more or less pots, then you'll see if you've found a better or worse skill combo.
I use a separate PVE and PVP build, but I haven't found a build that's better against bosses than my farming build. I feel like maybe Kzarka could use a separate build, and Arena/Ramoness might be better with separate builds...I'm still working it out tho.