It's only complicated on the surface because the game does a real shit job of organizing vital information to the player. It buries so many helpful elements under menus and in a very inelegant manner. Analyze for instance...why isn't the key information displayed in the attack cone targeting screen instead of hidden in the menu once successfully cast?
I've nearing the end of my fresh play(25+ hrs) still -only- using my three weapons and against any given enemy I can pull off extremely damaging hits, regardless of class, affinity, and type without ever grinding.
Basically my loadout is(all 1-handed):
-Edged sword(mostly against humans or one-off creatures/bosses weak to edge)
-A basic Iron rapier(Obviously for Piercing, but mostly useful for dragons, phantoms)
-Blunt Mace(Upgraded from the starter axe with a single combination to make it blunt. The second half of the game is full of blunt weak stuff, and the starter axe probably built up a decent light affinity fighting those bats and wolves, which is often useful against blunt weak enemies I've found.)
You -can- go nuts and have the full complement of 8 available weapon slots dedicated to unique breeds and enemies, but that just is just punishing yourself with limited inventory space and excess menu fiddling, for what amounts to little overall damage benefits. Especially on a first play through.
You really don't need to focus on the class type(human, beast, etc...) that stat has the weakest benefits compared to element and blade type(shame that the interface always shows Class page first on equipment status, making it seem most vital...but it isn't). Sure a 75 Undead stat will do decent damage to undead, but that same enemy might be weak to air, and a quick air-gem slotting and an air-buff spell to your weapon will do SO much more at 75 than the 'Undead 75' will. Bottom-line, the class bonuses pale in comparison to element damage, which is far more malleable to adjust on the fly with gems and spells(instead of grinding unique weapons). Which is why you only need the three basic weapons(preferably 1-handers to keep the shield for huge defense help).