Just another Whedon whore adding his two cents.
Buffy really found its stride in Season Two. Early episodes suffer from the creature of the week syndrome, but you’ll want to watch all of them because the history builds on itself. The dialog is wonderful, even in early episodes, that’s just something Joss has always been good at. The actors grow into the roles and the characters and their relationships develop into something a lot deeper. By the time you hit the later seasons, there is so much backstory that a simple phrase, sometimes even a look, can remind you of prior episodes.
I could ramble on more, but suffice to say, I recommend this show highly. Stick with it and you won’t regret it. As for Xander, he improves muchly by Season 2 and by 3 he’s great in his role. In Season One’s “The Pack”, you’ll see a hint of it. By Season Two’s “Halloween”, you’ll like him. When you get to a Season 3 episode called “The Zeppo”, you’ll love Xander. He’s awesome.
Like so many others have expressed, I wish I could forget them all simply so I could go back and watch them all anew. Even so, I’ve watched the entire series about four times, and many individual episodes much more than that. Enjoy!