improved

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:background="@color/second_grey"
    tools:context="com.favega.groups.MainActivity$PlaceholderFragment">

    <LinearLayout
        android:orientation="vertical"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:layout_alignParentBottom="true"
        android:layout_marginBottom="244dp"
        android:weightSum="1">

        <RelativeLayout
            android:orientation="horizontal"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_alignParentTop="true"
            android:layout_alignParentLeft="true"
            android:layout_alignParentStart="true">

            <TextView
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:text="Deportes"
                android:textSize="24dp"
                android:id="@+id/textView"
                android:layout_alignParentTop="true"
                android:layout_alignParentLeft="true"
                android:layout_alignParentStart="true" />

            <Button
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="VER MÁS"
                android:background="@drawable/blue"
                android:textSize="12dp"
                android:textColor="@android:color/white"
                android:id="@+id/button"
                android:layout_alignParentTop="true"
                android:layout_alignParentRight="true"
                android:layout_alignParentEnd="true"
                android:layout_marginRight="12dp"
                android:layout_alignBottom="@+id/textView" />
        </RelativeLayout>

        <LinearLayout
            android:orientation="horizontal"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:paddingTop="4dp"
            android:layout_weight="0.65"
            android:weightSum="0.99">

            <RelativeLayout
                android:layout_height="match_parent"
                android:background="@drawable/card"
                android:layout_width="0dp"
                android:layout_weight="0.33">

                <ImageView
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:padding="8dp"
                    android:id="@+id/imageView"
                    android:src="@drawable/img_football"
                    android:layout_alignParentTop="true"/>
            </RelativeLayout>

            <RelativeLayout
                android:layout_width="0dp"
                android:layout_height="match_parent"
                android:background="@drawable/card"
                android:layout_weight="0.33">

                <ImageView
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:padding="8dp"
                    android:id="@+id/imageView"
                    android:src="@drawable/img_football"
                    android:layout_alignParentTop="true"/>
                </RelativeLayout>

            <RelativeLayout
                android:layout_width="0dp"
                android:background="@drawable/card"
                android:layout_height="match_parent"
                android:layout_weight="0.33">

                <ImageView
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:padding="8dp"
                    android:id="@+id/imageView"
                    android:src="@drawable/img_football"
                    android:layout_alignParentTop="true" />
                </RelativeLayout>
        </LinearLayout>
    </LinearLayout>

</RelativeLayout>