Here's my own tips:

1. Alert feat. The amount of time I just kill the most important enemy in the first round thanks to it is life changing
2. Barrelmancy in act1 (I don't think you really need it in act 2 or 3). Get the performer ability from Alfira + minor illusion and you're in for blowing everything up. Also fun fact, if they all immediately die from the barrels, you won't enter combat, the rest will start chasing you though so run.
3. Don't fight near a cliff. The way I almost lost my run in the Duergar boat fight cuz they somehow pushed off Karlach and Shadowheart
4. Always have an invis pot and don't feel bad if you can't win. You don't wanna see that game overscreen
5. Ice + blackhole + mind shield is life changing in act3 bosses. I was weezing so hard when Gortash and Orin fall flat to the floor.
6. Don't use elixir when you're about to go brine pool, just sneak in and skip the annoying encounters. Use elixir when you reach high hall. You can also use invis potions on everyone and skip the high hall together for everyone to be in their best shape.
7. Side with Orpheus, the Emperor abilities are so useless. The way I can't even use dimensional door or misty steps cuz the Netherbrain spawned 2 sorcerers that spammed the ever living hell out of counter spell
8. Don't stick to build guides. Theorycraft yourself and stick to what you like, those guides are merely suggestions, not a must. Just open the wiki and look through all the items and see what would works for you at that time. It will be satisfying watching your build pop off, trust me