There’s a small caveat in Magic: you can only pay any given cost for one ability or spell; you can’t use the same cost to pay for two separate abilities. That’s just not how life (or Magic) works.
Very simple here with the Cluestones. Since the Cluestone’s abilities require it to tap for both the mana and the card drawing, you can’t tap it once to fulfill both abilities (unless the Cluestone became untapped somehow from another ability). If you tap it for mana, you won’t be able to tap it to pay for the sacrifice ability. So you’ll need mana from other sources in order to fully pay for the ability that draws you a card.
Today’s Rules Tip written by Eddie Cheung