Is Sasuke a main character in Naruto?

No, Gaara is actually a side character in the anime series Naruto. Naruto, is of course, the main character appearing in the series. Gaara first makes his appearance when Naruto is sent off for Ninja testing. He is from the village hidden in the sand.

So all in all,

- Main character: Naruto Uzumaki.

- Gaara: Side character.

~no. the main character in naruto is naruto obviously. they don't intruduce gaara until the chunin exams in like episode 30 or even 50. but in the first season of naruto shippuden, the season is all about getting gaara back from the akatsuki.