I suggest you to use Tier-I Archers for resource gathering because:
They travel faster. Speed = 4
They have good capacity. Capacity = 6
They are cheap to produce. Might = 2
In addition, they can serve as a good defending army.
The Capacity and gathering speed can be further enhanced by switching to particular type of gear and talents points.
Although resetting Talent points cost a lot of coins, so you can avoid resetting Talent point every time.
Narceros Gear is the best and recommended gear for resource gathering. Higher the level of resource tile means faster the gathering. So always prefer to sit on higher level resource tiles to save your time.
Hope this will help you for good gaming experience.
Disclaimer: The information is based on personal experience. A small negligence can cost you big. It is advisable to learn before you start investing your time and money.