I think, like a lot of people, my first exposure to Dropout's stuff was on youtube. There's a lot of stuff you can watch for free before paying for it, and Sam makes a point of keeping everything affordable and customer-friendly.
For Game Changer, watch the first Sam Says episode to get a sense for the tone.
For Make Some Noise, you can just check out their clip channel and look at... Any of them. There's no continuity to worry about.
For Um Actually, there's an episode about D&D that, as a D20 fan, you should be able to play along with.