Gond Gate has the ability to make your Gate lands more powerful by allowing them to enter untapped, and when it is tapped, it also grants you a single mana that one of your controlled Gate lands could produce
Control decks or anyone else who wanted to keep a full hand had no choice but to deal with it, or they couldn't play their game
That's all well and good, but the real draw with Ruby is that she can tap for either green or red mana
Sure, your opponent might have ten beasts in their green deck, but Callous Oppressor would still be able to steal their four goblins, three elves, and two other creatures that weren't beasts
Whether Raul is your Commander, or just helping make your mill deck flow smoothly, theres a lot of power to be had here