Recyclerview first item start margin

Add padding to your RecyclerView and Use

android:clipToPadding = "false"

inside your RecyclerView, to disable padding while scrolling it.

<android.support.v7.widget.RecyclerView
        android:id="@+id/rv"
        style="@style/WrapContent"
        android:layout_marginTop="16dp"     
        android:padding="16dp"
        android:clipToPadding = "false"
        app:layout_constraintTop_toBottomOf="@id/tvFoo"
        tools:layoutManager="android.support.v7.widget.GridLayoutManager"
        tools:listitem="@layout/item_foo"
        tools:orientation="horizontal"/>