I need some tips

So i took a fairly long break from the game (over half of SL and the entirety of DF), so im rusty.

Mainly want some refresh regarding combo expending as Sin, i often feel i fall behind far more than i should in dmg.

Im using the talents that increase my cap at 7, but should i go out of my way to reach 7 points? or just expend once i get 5?

Obviously theres situations like the free Ambush where i can aim for higher for free, or filling the last two combos with the likes of Garrote, Shiv and Kingsbane when theyre up.

Should i hold off on expending points while Envenom buff is up and mainly focus on refreshing it?

Any other suggestions are welcomed.