So the low-grade Art-users - is this the equivalent of cantrips and such? Hedge magic? Minor healings, divinations and good luck charms?
Also, what's the situation with regard to enchanting items? Are our more talented followers able to imbue objects with the Art on their own? Is there some way to make this process easier for them?
I am thinking in the general direction of working towards a kind of industrial revolution that combines technology and the Art, with minor life-improving enchanted items being more-or-less ubiquitous. F'rexample, enchanted hearthstones that flicker with magical fire on command, growing hot enough to warm a house and cook food without need for fuel. Likewise lanterns and lightsources, boxes or charms that preserve foodstuff from decay, maybe enchanted rocks that, when placed around a field, will encourage the bountiful growth of crops within the bounded area.
If we can make our people successful and prosperous by teaching them such things, non-believers will hear about it and flock to us. Provided we make it clear that we are also strong enough to defend what is ours, we should see a pretty steady stream of people wanting to join up.