Keep it simple and pick a dual class based on (1.) how you like to play; (2.) preferably a class that can use most of the same equipment as your main to save you adena; (3.) that is quick to level; and (4) has no problems getting groups.
In some respects picking the right dual class is even more important that picking your main. I know lots and lots of people who no longer play their main class and spend most of their time as their dual class. Take your time and weigh your choices.
Gear-sharing is not that important because:
1. It is not worth playing a class you don't enjoy to save money.
2. Most of the expensive gear is in your epics, brooches, talismans anyway.
If you don't see another class you are DYING to play, then consider a support class like Iss or healer, so you can help your clan during raids and sieges when the usual support people are all busy irl. If you despise playing support class however, Wynn is easiest, cheapest, and no one will really ever ask you to play it over your archer. But support is a better choice "for the team".
On a personal note, I deleted my Archer's Wynn dual (it was 99!) and went Iss, because the Wynn simply wasn't useful enough for what I could offer to the team.
A Feoh would probably be the worst choice because the gear is very different (ruby v sapphire, strong retributer, only robes, etc)
So, im gonna play dagger..cuz i like it and it will share equips
The only problem is hard to get xp and group i think...but lets see what happens
Ty guys