Outside of adding new special attacks, how much stronger did Luffy, Zoro and Sanji get between their introductions and the start of Arabasta

[Warmmedown]

They fought all these enemies from the crews of Buggy, Kuro, Don Krieg, Arlong, Baroque Works, Wapol. But for example, Luffy could fight Arlong just fine and only needed a new special attack to defeat him. He couldn't break Krieg's armour but then defeated him with a more powerful special attack. Kuro he could easily hurt if he hit him, but his speed was far above anyone in East Blue. These were all Grand Line pirates.
Outside of adding new special attacks did they get much stronger?