I don't recommend you watch all episodes from the start to the current, In fact I actually recommend you watch anything that isn't filler (E.G New catches, evolutions, anything plot related (E.G Evil organizations), league battles, contests (AG and DP only) and gym battles) Here's a run down of episodes you should watch
Episode 1 - Pokemon, I choose you (Introduces Ash, Misty, Gary and Pikachu)
Episode 2 - Pokemon Emergency (Introduces Team Rocket)
Episode 3 - Ash catches a Pokemon (Ash catches his first pokemon, Caterpie)
Episode 5 - Showdown in Pewter City (Introduces Brock, Ash wins the boulder badge)
Episode 6 - The water flowers of Cerulean City (Ash wins the Cascade badge)
Episode 10 - Bulbasaur and the hidden Villager (Ash gets bulbasaur)
Episode 11 - Charmander - The stray Pokemon (Ash gets charmander)
Episode 12 - Here comes the squirtle squad (Ash gets Squirtle)
Episode 14 - Electric shock showdown (Ash battles Lt. Surge and manages to win the Thunder badge)
Episode 21 - Not spoiling this episode
Episode 24 - Haunter vs Kadabra (Ash battles with Sabrina and gets the Marsh badge)
Episode 25 - Primape goes bananas (Ash catches Primape)
Episode 26 - Pokemon scent station (Ash gets the rainbow badge)
Episode 27 - Hypno's naptime (Misty gets psyduck)
Epiosde 28 - Pokemon Fashion flash (Brock gets vulpix)
Episode 29 - Not spoiling this episode
Episode 31 - Dig those diglett (Jessie's Ekans and James' koffing evolve into arbok and wheezing)
Episode 32 - The ninja-Poke showdown (Ash battles with Koga and gets a Soul badge)
Episode 44 - The attack of the prehistoric Pokemon (Ash's charmander evolves into Charmeleon and also evolves into charizard)
Episode 48 - Who gets to keep togepi (Misty gets togepi)
Episode 55 - The breeding center secret (Introduces Cassidy and Butch)
Episode 56 - Riddle me this (Ash vs Blaine 1)
Episode 57 - Volcanic panic (Ash vs Blaine 2, Ash gets the Volcano badge)
Episode 61 - Battle of the badge (Ash gets the earth badge)
Episode 70 - Go west young meowth (Not really important but it shows alot of meowth's past)
Episode 74 - episode 80 - The first pokemon league
That's most of the important episodes in the original season