Caesar Clown is a skilled fighter, but it’s mostly thanks to the fact that he has a very powerful Devil Fruit. Luffy is easily superior in terms of battle experience and he’s a better hand to hand fighter. Once he lands a solid hit on Caesar Clown, the match will essentially be over. Caesar’s durability isn’t great so it will be tough for him to get up from such an attack and his speed isn’t as impressive as Luffy’s either. Luffy wins.