for a quick rundown every enemy has three factors that affect the damage Ashley can deal to it: affinity, elements, and damage types. Golems, being made of rock are rather resistant to piercing and edged weapons so you will do a LOT more damage if you pull out a nice blunt instrument. There are two available before you reach the Golem if you've been looking everywhere.
affinity is the easiest thing to get, but also seems to have a lower effect than the other two. for instance the final boss is evil type but has 90 resistances to both light and dark elements, so even if you have a high evil weapon if it deals light or dark damage it will still be resisted heavily. Element is a significant factor in damage and it's easy to mod on the fly through gems and fusion spells. Damage type is going to be a deciding factor much of the time. Most enemies have a paticular damage type they are weak/strong to so you have to carry a variety of weapon types so you can adapt to your foes weaknesses. Some trends run though the enemy types (such as most dragons are weak to piercing and resistant to blunt) but you should always remember the analyze spell. it gives a wealth of info and can really get you out of tough spots.
Sanity's really just a one trick pony, you just get one trick: rational thought. But when you're good and crazy, oh baby! The skies the limit! - The Tick