Things worth watching
Mabel's Strange Predicament (1914)
The short for which Chaplin went rummaging around in the studio wardrobe and created the tramp's costume. The Mabel of the title is Mabel Normand, who was quite the movie star in her day; she specialized in madcap Keystone Kops-style comedies like this one, where she scampered around the set scandalously dressed only in her lounging pajamas. The tramp is not much of a hero here -- he lacks the romanticism and plucky altruism that characterizes him in later films. Chaplin has already got the walk, though, and a less fine-grained version of the mugging.
The Immigrant (1917)
By this time, Chaplin was writing and directing his own films as well as starring in them. They're all more or less the same thing, thematically; if you like the first few, then the rest are worth watching. The little tramp has by now become a sort of itinerant do-gooder, sticking up for the downtrodden and helping out a girl he's gone head-over-heels for even though he thinks he'll never see her again, and she'll never know who it was. Because of the lack of dialog and the very limited space in the intertitles, these things also depend heavily on the viewer recognizing familiar social signs to understand the plot. Most of them have aged pretty well, but this provides one of the rare examples which hasn't. When the tramp accidentally meets the lady again in the restaurant, she's terribly sad. He indicates he wants to know why and when she starts to dab at her eyes he shows understanding, at which point modern viewers get confused. At the time it was the custom to carry black-edged handkerchiefs when in mourning -- clearly her mother, who was quite ill on the boat, has passed away. It's easy sometimes to get stuck on stuff like this, where if you don't already know what's going on here it's next to impossible to even guess which detail is supposed to be important. Context is key.
The Gold Rush (1925)
This feature film is the source of two of the best-known clips of Chaplin, the infamous bit where he's so hungry he boils and eats his own shoe, and the one where he sticks forks in a couple of dinner rolls and makes them do a little tap dance on the table. This edition is a 1942 sound re-edit and re-release of the original silent version, from which he has snipped the intertitles and to which he has added narration. The voiceover is Chaplin in his stage-announcer-narrator voice, which is somewhat different from his ordinary speaking voice.
Chaplin was notorious for hating early talkies. He was unimpressed with the sound quality, to put it mildly. He always contended that the moment the tramp talked, it would ruin the character. That's not entirely true. The tramp isn't mute within the context of his films -- he talks to the other people in the story, it's just that we can't hear him. You can catch most of his lines if you lip-read. Chaplin is pretty easy to get, despite the mustache, as is Georgia Hale here; the other characters are progressively less so, starting with the other dance hall girls and working down to the bearded, mumbling prospectors. The narration is a combination of quoting and paraphrasing what's said on screen. The tramp has a name here, although it's never mentioned aloud: When he's dreaming that the girls have come to dinner with him, Georgia calls him "Charlie". I presume Chaplin dug the exact dialog out of the continuity script (it's mixed in with shot descriptions and stage directions on his edit sheets), read lips as well as or better than I do, or just had a fantastic contextual memory for a film he'd made fifteen years before.