All you need. Nothing you don't.
Churches are not planted, nor are they started, nor are they birthed, etc. The moment we endeavor to plant or start a church we enter again into the realm of insitutionalism. Christians simply meet as the church.
A church, we have observed, simply means a gathering, group, or an assembly. A church of Christ, we learn from the Scriptures, consists of believers statedly assembling together to enjoy the benefits of association. These benefits are not limited to any number. Even two can associate together. They can mutually assist, admonish, or reprove each other. When the Lord commands his disciples not to forsake the assembling of themselves together, he requires that they should associate as far as they have opportunity, and no farther. The precept is as binding on two as upon two hundred. These can co-operate, and continue steadfastly in the apostles’ doctrine, fellowship, breaking of bread and prayers; and the abundance of the one may be a supply for the other’s want. It is, I believe, generally admitted, that two or three disciples residing in the same place should meet together, and observe every ordinance, except the Lord’s supper.
But we find no limitation as to the number of a church in the Scriptures; nor any thing to countenance the stated association of the disciples in any other form. Besides, what is there peculiar in the ordinance of the Lord’s supper, that the churches, while attending to every thing else in their power, should delay the observance of this till they obtain elders to administer it? This idea of administration is very consistent in the church of Rome, or of England, where each individual receives the elements from the Priest; but in this country, both in the Establishment and among Independents, each member administers it to his neighbor; that is, puts the bread and the cup into his hand. If the elder administers it to those nearest him, they, in their turn, administer it to him; so that the idea of laying any stress on an administrator is utterly inconsistent, besides leading to the unfounded supposition, that the administrator represents the Lord Jesus Christ, in which case he ought not himself to partake.
The plea for the necessity of an elder or officer being present at the Lord’s supper, surely originates in some mistake respecting its nature. It must be supposed that it is similar to the sacrifices under the law, which could only be offered by a Priest, or that it contains a mystery still unexplained; and if transubstantiation be given up, something analogous is substituted in its place. Let the reader compare and consider with attention the passages in which this institution is described, and he will be convinced that this view has no foundation.
No good reason then can be given why two or three believers, who have not an opportunity of meeting with a greater number, should not statedly assemble as a church of Christ, to observe the Lord’s supper, as well as to continue in the apostles’ doctrine and in prayers. Indeed it is their bounden duty to do so. It certainly cannot be shown that elders or deacons are essential to the existence of a church, while we find the apostles returning to Lystra, Iconium and Antioch, and ordaining elders (i.e. appointing elders or older ones to be the shepherds or pastors) in every church, Acts 14:21,23, which they had previously gathered. Indeed, from the very nature of the case, churches must exist before elders, out of which they arise.
The apprehensions that the consequence of two or three observing the ordinances of Jesus, will be their remaining at home, and not assembling in any considerable number, nearly resemble those of the consequences of eating the Lord’s supper without elders, which, it is alleged, sets aside the elder’s office. But as long as men regard the authority of Jesus, they will consider themselves bound, after the example of the first churches, to assemble statedly with as many of their brethren as local circumstances might permit. And if ever His will, so plainly signified, loses its effect upon their minds, it is a matter of little consequence whether they have them (i.e. officers) or not. Their eating the Lord’s supper at all, must in that case, arise from superstition, and not from Christian principle.
Observations on Various Subjects, J.A. Haldane, published by John Ritchie, 1808. pp. 12 – 15.