The Mesh class gives you 6 arrays:

• .vertices
• .colors
• .normals
• .tangents
• .uv
• .uv2

to specify your vertex-data. Each of those array, if they are used, have to have the same size as the vertices array. So colors[4] will be the vertex color of your 5th vertex and belongs to the position in vertices[4].

Those 6 arrays work as one array and define your vertices.

The triangles array hold indices to those arrays above to form triangles. The size must always be a multiple of 3 (since a triangle have 3 corners).

I'm not quite sure what's your actual problem... Do you have trouble to fill your uvs? Noone can help you here. UVs are normally created by the artist during unwrapping. If you create all dynamically you have to know how you need them...

An example to use the x,y coordinates as UVs:

var myVectices : Vector3[]; // you have created your vertices already and stored in this array

var myUVs : Vector2[] = new Vector2[myVectices.Length]; // Create array with the same element count
for(var i = 0; i<myVectices.Length; i++)
{
    myUVs[i] = Vector2(myVectices[i].x,myVectices[i].y);
}

It doesn't make much sense in most cases to use the x,y values directly (except they are within 0..1 or you have a tiled texture)

Just use a for loop (assuming you have some kind of way of generating your uv coordinates for a given x,y,z vertex location). I just used Sin and Cos here.

var uv = new Vector2[1000];
for (var i = 0; i < 1000; i++) {
    uv[i].x = Mathf.Sin(i / 1000.0f);
    uv[i].y = Mathf.Cos(i / 1000.0f);
}

mesh.uv = uv;