With great teachers you're able to kick some ass. Furthermore Naruto got good "genes". Think about daddy & mommy, they're damn great. I guess the chakra-reserve is not that unimportant. Come to think of it, he got much more chakra than Kakashi (just without fox).
Naruto is eventually able to solve problems with jutsus in a creative way. For example the Rasengan/Rasenshuriken with Shadowclones. At this point, let us remember,
at series start Naruto stole the forbidden scroll. He learned Shadowclone jutsu, which is more or less the basic of his jutsu development. What would've been when he had not learned that jutsu.
Thank god we will never know ^^