Below is the code for divider in RecyclerView with left margin. Just paste the code in your OnCreate method of MainActivity.
class SimpleDividerItemDecoration extends RecyclerView.ItemDecoration {
    private Drawable mDivider;
    public SimpleDividerItemDecoration(Context context) {
        mDivider = context.getResources().getDrawable(R.drawable.divider);
    }
    @Override
    public void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) {
        int left = 250;
        int right = parent.getWidth() - parent.getPaddingRight();
        int childCount = parent.getChildCount();
        for (int i = 0; i < childCount; i++) {
            View child = parent.getChildAt(i);
            RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();
            int top = child.getBottom() + params.bottomMargin;
            int bottom = top + mDivider.getIntrinsicHeight();
            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(c);
        }
    }
}
recyclerView.addItemDecoration(new SimpleDividerItemDecoration(
            getApplicationContext()));
Since, the divider.xml file will be missing from your drawable folder so below is the code that you have to paste on the divider layout after creating it on drawable folder.
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
  <size
    android:width="1dp"
    android:height="1dp" />
  <solid android:color="@color/divider" />
</shape>