Is there a guide for weapons as you level?

There is no level requirement for equipment so basically the best weapons are the same for any level

It would be hard to make a guide like that because the weapon choice would vary by class, build and personal style.

For instance, an Assassin with solo build starts out using nails/special bows until it has enough stats to change weapon to Throw while keeping up with the damage.
That same class with a spammer build would start out with Throw and never change or use a bow (normal or magical) if starting DEX before INT.

Some enchanter builds (like attack autoskills build) could start playing as a regular wizard/high wizard and use Staffs to cast spells then change to whatever weapon of their choice once they add agi for the aspd (magic sword, magic bow, throw, nail, basically any weapon they like, specially if it comes with a good autoskill).

Other classes might have builds that go through the same situation or that can use a specific weapon to compensate for something they only get later on (higher heals, spellburst, evasion, HP, Hate...) but the choice of weapon and when to change it is ultimately up to the player.