‘For we stretch not ourselves overmuch, as though we reached not to you, for we came even as far as to you in the gospel of Christ, not glorying beyond our measure, that is, in other men's labours, but having hope that, as your faith grows, we shall be magnified in you according to our province to further abundance, so as to preach the gospel even to the parts beyond you, not to glory in another's province in regard of things ready to our hand.'
We are not over-exaggerating what we are and what we have done, says Paul. We are not over-stretching ourselves in order to reach you, making claims that we have not achieved. For when none other had we did actually stretch out and we did reach you with the Gospel of Christ. We are not, like them, glorying beyond measure, that is, glorying in other men's labours, in what other men have achieved, what other men have reached, rather than in the measure of our own achievements. Rather our hope is that as your faith grows so it will reflect to our credit because it was we who led you to Christ. We will be vindicated by it. And we will thus be enabled to successfully and fruitfully advance further into the area that has been allocated to us by God, achieving even more successes, preaching the Gospel in places yet unreached, which are even further off from Jerusalem than you are (‘beyond you' - see Acts 1:8).
The idea may include that Paul having established the Gospel in the main city, his converts become established and take that Gospel outward to the surrounding areas.
His point is clear. These who boast in themselves are parasites. Not for them expansion into the unknown. They prefer to follow up others, poaching on what they have achieved. For they have no power in themselves to establish new churches. They can only pick other men's fruit, the fruit from other men's labours. They are not true Apostles. They are scrumping.
‘Not to glory in another's province in regard of things ready to our hand.' That is, not making our boast in what someone else has done and achieved, (like they do), not taking advantage of things ready to hand, plucking things with our hands that are easily available, and then claiming that we have somehow improved them. His words are derisory of those who make great claims for themselves and yet prove their inadequacy by not being able to achieve anything for themselves. In their self-conceit they can only act as spoilers.