The evolved axe is amazing!
I've had all my best runs in the library. I like getting garlic, bible, and whip. The three together give you a pretty good bubble to avoid being swarmed. As far as I can tell the bible works a bit like the garlic, but it depends on where exactly it's floating around you at a given time. The evolved fire will also make a difference and agree with the water. It's not always my first choice, but as you upgrade it and move with it's pattern it's great for getting gems. Whenever I can, I also grab spinach, the weapon duplicator, and area expansion. Anything that benefits all weapons is super helpful.
I 100% agree with choosing a few projectiles and focusing on upgrading them. It's tempting to just get all the things, but more focused damage from a particular weapon is better when things get hairy.