I personally would not skip any of them if you want to see Amanda, she just pops up every six episodes and then disappears again.

Methos appears in mid-season 3 and remains until the end, but he's recurring as well.

It helps to see them all to understand the backstory and what the heck is going on, but it's a show that is a lot less arcy than others we both watch, and so there are more filler eps.