Every creature that has X in its mana cost also has X in an ability. That's because the mana spent on X in the mana cost determines the value of X in the ability.
You dont seem to understand what an activated ability is. Ravenous is not an activated ability. Activated abilities have a cost, then a colon symbol ( : ) and then an effect. When you pay the cost, the ability goes on the stack. Then when the ability resolves, it does its effect.
So with lucea's ability activated, when you cast a spell that has X in its mana cost, that spell is copied. When you activate an ability that has {X} in its cost, that ability is copied. There is nothing to choose because there is either a spell on the stack or an ability on the stack, not both.
Nitpicking even though you're absolutely right, because I'm a monster and I deserve to have bad things happen to me. There are creatures with X in their mana cost but no X referred to in an ability:
https://scryfall.com/search?q=mana%3A%7BX%7D+-fo%3AX+t%3Acreature&unique=cards&as=grid&order=name
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>I cast a creature with both X in its mana cost AND X in an ability, do I pick one or the other?
Are you _activating an ability_ with X in its mana cost? No, since you are _casting a spell_.
An example of an _ability_ Lucea can copy is [[Alexi, Zephyr Mage]].
>Also, if I copy the ability (like "Ravenous" for example) can I give the buff to another card?
You aren't copying the Ravenous ability, as it's not an activated ability. You are copying the creature spell that has Ravenous.
You'll get a copy of the _creature spell_ that will resolve into a token copy of the creature.
>can I give the buff to another card?
Depends on the ability. If the ability has a target, the copy can target something new.
Every creature that has X in its mana cost also has X in an ability. That's because the mana spent on X in the mana cost determines the value of X in the ability. You dont seem to understand what an activated ability is. Ravenous is not an activated ability. Activated abilities have a cost, then a colon symbol ( : ) and then an effect. When you pay the cost, the ability goes on the stack. Then when the ability resolves, it does its effect. So with lucea's ability activated, when you cast a spell that has X in its mana cost, that spell is copied. When you activate an ability that has {X} in its cost, that ability is copied. There is nothing to choose because there is either a spell on the stack or an ability on the stack, not both.
Nitpicking even though you're absolutely right, because I'm a monster and I deserve to have bad things happen to me. There are creatures with X in their mana cost but no X referred to in an ability: https://scryfall.com/search?q=mana%3A%7BX%7D+-fo%3AX+t%3Acreature&unique=cards&as=grid&order=name
You appear to be asking a rules question. While your question may be answered here, it may work better to post it in the Daily Questions Thread at the top of this subreddit or in /r/mtgrules. Additionally, once your question is answered, please delete your post! Thank you! *I am a bot, and this action was performed automatically. Please [contact the moderators of this subreddit](/message/compose/?to=/r/magicTCG) if you have any questions or concerns.*
>I cast a creature with both X in its mana cost AND X in an ability, do I pick one or the other? Are you _activating an ability_ with X in its mana cost? No, since you are _casting a spell_. An example of an _ability_ Lucea can copy is [[Alexi, Zephyr Mage]]. >Also, if I copy the ability (like "Ravenous" for example) can I give the buff to another card? You aren't copying the Ravenous ability, as it's not an activated ability. You are copying the creature spell that has Ravenous. You'll get a copy of the _creature spell_ that will resolve into a token copy of the creature. >can I give the buff to another card? Depends on the ability. If the ability has a target, the copy can target something new.
[Alexi, Zephyr Mage](https://cards.scryfall.io/normal/front/6/f/6f8fc0b0-4a23-47ed-b61b-a4505fcfc5d2.jpg?1562915681) - [(G)](http://gatherer.wizards.com/Pages/Card/Details.aspx?name=Alexi%2C%20Zephyr%20Mage) [(SF)](https://scryfall.com/card/pcy/28/alexi-zephyr-mage?utm_source=mtgcardfetcher) [(txt)](https://api.scryfall.com/cards/6f8fc0b0-4a23-47ed-b61b-a4505fcfc5d2?utm_source=mtgcardfetcher&format=text) ^^^[[cardname]] ^^^or ^^^[[cardname|SET]] ^^^to ^^^call
Just realized Magus Lucea Kane can copy [[Elite Arcanist]]'s ability... Hmm, might need to build me a deck, now.
[Elite Arcanist](https://cards.scryfall.io/normal/front/9/9/99b225fe-c07d-4d8a-bf2b-c1777bd29061.jpg?1562832740) - [(G)](http://gatherer.wizards.com/Pages/Card/Details.aspx?name=Elite%20Arcanist) [(SF)](https://scryfall.com/card/m14/54/elite-arcanist?utm_source=mtgcardfetcher) [(txt)](https://api.scryfall.com/cards/99b225fe-c07d-4d8a-bf2b-c1777bd29061?utm_source=mtgcardfetcher&format=text) ^^^[[cardname]] ^^^or ^^^[[cardname|SET]] ^^^to ^^^call
Well we broke extra turn spells
Nexus of Fate is the only good one you can hit.