To be honest, you can omit the majority of fillers, although some are entertaining or provide interesting character moments. These are the ones that I think are worth seeing:
"Gotta See!" in episode 101 You Must Know! The Real Face of Kakashi-Sensei! (Hilarious classic)
Kurama clan storyline, good plot, and passion in episodes 136–141
The last pre-Shippuden episode, episode 220, provides a satisfying conclusion.
Parts of Episodes 176–196 If you enjoy the team chemistry, a few lighthearted, humorous missions are worthwhile.
Unless you simply want more Naruto world content, you may skip the rest.