Ascendancy
For leveling, Invoker is currently the best Ascendancy for the Monk. Invoker offers utility and power without requiring extensive endgame investment, making it ideal for Path of exile currency standard leveling.
I am the Thunder: Grants you shocked ground for easy shock application, perfect for generating Power Charges with Siphoning Strike.
And I am the Storm: This increases your damage significantly during boss fights, boosting your overall DPS.
Lead me through Grace: This will help you generate Spirit at later stages, increasing your Energy Shield and survivability in tougher fights.
Equipment
Quarterstaff:
Physical Damage and Flat Physical Damage are essential for Falling Thunder scaling. Look for items that provide Physical Damage as a base modifier, ideally with crit chance and POE currency for sale crit multiplier.
If you can't find a high-tier Quarterstaff, you can use any weapon with decent flat physical damage until you get a good one.