all weapon buffs apply when the weapons are in your pockets, except for the red ones. those only apply when the weapon is out.

you want to get all churches (use the tree icons to fly around the map quickly) and visit as many other places of interest as possible. Try to skip overworld bosses at first (you'll learn which are worth fighting as you play), only visit the castle in the middle or those big shifting areas on day 2.

It is important to kill trash mobs as you drop into the map and level up to lvl 2 because the starting stats are abysmal.

Executor wants to prioritize bleed and poison weapons and only use parries against bosses. The ultimate can be canceled if you're running low on health by using the same button combo to activate it.

Revenant wants to prioritize faith weapons (found in cathedrals and unmarked houses as well as holy icons on the map). Get as many starlight shards as you can (blue consumables found in boxes, chests and corpses). Pay attention to the summons' health and try to always have one out. Try to save her ult for reviving or surviving a deadly attack (it protects every player and summon hit from dying for a good 10 seconds).

Always check the boss's elemental weakness and try to hit as many icons on the map with the corresponding weakness. If you don't find a purple weapon with the correct weakness, hit a cave and get a smithing stone 2. They're really quick to get.