Yeah it was either too hard or too easy. I couldn't find the right balance. LOL. Jiro is correct!

It's all dexterity & luck
Reference to stealing. Also I know luck helps, dexterity might too, in increasing the chance of stealing. At least I believe both stats get raised when equipping the steal materia

To climb this challenging cliff
Again I gave away the answer with this hint. Challenging = hard, cliff = edge.

All it takes is one pluck
Another reference to stealing. It only takes on try to get it!

You might try 3 times and whiff
There's a subtle reference to who you steal it from. 3rd class Soldier in the Shinra Building after you are released from the prison cells

The real full answer was Stealing the Hardedge from 3rd Class Soldier but that's close enough. Go for it, Jiro!