I'll preface this by addressing the suggestion to pick up a lance.
Knowledge is power. We have the ability to look into the future and we know that Mabinogi is going to receive an overhaul of the melee combat system. Take a little bit of time and review that information. That will give you the insight needed to make an educated decision as to the way forward.
Lances are well understood to be an effective weapon system. The ability to cleave through enemy protection should not be underestimated. That being said, I would advise you to ignore Lance Charge. It's not a bad skill by any means but it's not worth the hefty reforge investment that numerous other players have made as of late. Smash and Windmill are, at present, the quintessential melee skills. If anything, you should be focusing on those.
At this time, duel-wielding is effectively obsolete. While the renovation update will improve numerous aspects of dual-wield combat, you will still face the added difficulty of reforging, upgrading, enchanting, and maintaining two weapons as opposed to one. I'll now briefly cover some dual-wield options which you should consider. There are other semi-viable options which may be superior but suffer from heavily bloated initial/sustainment costs. These include things like demonic swords, apostle swords, spirit weapons, caladbolg, and elsinore.
Rainbow Beam Sword:
- Pre-enchanted w/Shadow Hunter and Spike
Note: This is your fire and forget weapon. Falls off sharply as your character develops but god damn that's a lot of max (204)
Falcata:
- Pre-reforged
- Eligible for special upgrades
Note: A decent weapon and likely the most useful of its ilk but I would look onward.
Royal Celtic Sword *Unreleased*
- Eligible for special upgrades
- Grants a whopping THREE set effects (Bash Damage, Critical Damage, and Durability Reduction)
Note: If you're really interested in dual-wielding, this is going to THE weapon to do it with. The initial investment will be steep but you will regret dropping gold on anything else when these come out.