I thought I should make all index/vertex buffers of a fixed size,but just now,at the end i realize the big problem.

If I have a mesh that is in 2 vertex buffers,but it's indices in 3 index buffers,how do i deal with that?

Because someone said nvidia recommends 2mb per buffer.I said what I'm gonna do? create buffers based on what?

And everybody said that you shouldn't create 1 buffer per mesh,so i created a simple algorithm that nests multiple meshes untill it fills the buffer(the same for indices).

Now i'm in big trouble cause i can't figure how to draw everything!

You can append some index data to the vertex structure such that all vertices that belong to the same mesh will know what world matrix to use, and what skeleton hierarchy to VTF etc. You gotta use triangle lists for this I think. This way you can draw the whole buffer (with many meshes) in one drawcall.

My suggestion would be that unless you're having performance problems, stick with one vertex buffer and one index buffer per model.

In most cases, you don't gain that much performance by packing the data from multiple models into one buffer, and it makes your code significantly more complicated.