在Laravel 5.7中以“州” - >“城市” - >“市政”的方式进行相关输入

I'm trying to make a form that contains 3 inputs. The first one should let the user select a state. Now, based on that selection (selection of input 1), the second input should load data from a DB table that has a relationship with the selected state, and the third input doing the same but in relation of the second input selection.

I have no idea how to do it, though I've tried this way:

My view: (it's all wrong here, I guess the magic happens on the controller).

                <div id="inputs-estado">
                    <div class="form-group">
                        {{-- Estados --}}
                        <label for="">Estado</label>
                        <select name="direccion" id="forma-estado" class="form-control dynamic" data-dependant="state">
                            @foreach ($estados as $estado)
                            <option value="{{ $estado->state }}">{{ $estado->state }}</option>
                            @endforeach
                        </select>
                        <br>
                        {{-- Municipio/Delegación --}}
                        <label for="">Ciudad</label>
                        <select name="direccion" id="form-ciudad" class="form-control dynamic" data-dependant="city">
                            @foreach ($estados as $estado)
                            <option value="{{ $estado->state }}">{{ $estado->state }}</option>
                            @endforeach
                        </select>
                        <br>
                        {{-- Colonia --}}
                        <label for="">Municipio</label>
                        <select name="direccion" id="form-municipio" class="form-control dynamic" data-dependant="municipality">
                            <option value="">Selecciona el municipio</option>
                        </select>
                    </div>
                </div>

My controller:

public function fetch(Request $request)
{
    $state_id = DB::connection('db_postalcodes')->table('city')->get();
    $select = $request->get('select');
    $value = $request->get('value');
    $dependent = $request->get('dependent');
    $data = DB::connection('db_postalcodes')
        ->table('city')
        ->where($select, $state_id->state_id)
        ->groupBy($dependent)
        ->get();

    $output = '<option value="">Select ' . ucfirst($dependent) . '</option>';

    foreach ($data as $row) {
        $output .= '<option value="' . $row->$dependent . '">' . $row->$dependent . '</option>';
    }

    echo $output;
}

Also, I've got multiple tables with the data stored. So I guess I need to use some relationship functions in Laravel (but I don't know).