I've read a fair few webcomics. I find the art in the comic good, strong style and visually memorable. Like any art there's room for improvment, but it communicates well and doesn't distract.
As for the actual writing/content/etc. You've decided to go for a set of one shot comics, with vague continuity. Not a bad format, but it requires you put more effort into each individual comic to make it stand up on its own.
Bitcoin Mascots - I found this cute, it actually had personality behind it and a setup people could understand. I actually expected the two people talking would become recurring characters.
Bitcoin Rate - Kinda a "slice of life" thing here. It expresses a real life event in a slightly exaggerated way to make it's point. It's fine for communicating what happened, but there's not humourous twist or really any comedy to it; more like "look what happened to me".
If people are interested in what happened, that's fine, if they're not, there's nothing in the comic to pull them in.
It's also a little awkward as the Bitcoin rate will have a very turbulent future, so after a steep dive (like the recent one from $30), it's harder to accept this comic.
Bitcoin Future - Here you basically imagine what the future will be like and express how the established order of things could be inverted.
That's kinda it really.
Bitsquirrel - I actually find this one kinda cute and funny. It's reliant on people understanding the values of the increase in bitcoins though.
The Gavinator - Kinda reads like a propeganda poster.
Fiat Kingdom - Kinda your worst one. It's basically pushing across your political beliefs without anything to back it up.
The positives:
You are making the comic, you wish to improve, you can write the occasionally funny line and take inspiration from the Bitcoin community and while not everyone may like it, it has a decent quality to it though nothing amazing.
The negatives:
The comic fulfills the criteria of "comic for people who want to read comics involving Bitcoins" and contributes to the Bitcoin culture, but it dosn't do much more than that.
There are a couple of styles that the comic approaches, but doesn't do well enough in any of them.
If you wish to make it more funny and "gag-a-day", you need a more humour with wittier dialogue and funnier scenarios, the objective should be to make the personal laugh a priority.
If you wish to make it more "this is my vision of Bitcoins", expect not everyone to go for it, but compensate but making the scenarios you envision(Bitcoin Future for example) richer with more detail and atmosphere to communicate what you imagine Bitcoins to be.
If you want to make it more political (Fiat Kingdom), you need to improve your sense of wit and social satire including more detail arguments and insights into the statments you are trying to make.
It'll take you a bit of time to find the style of comics that suit you best, but my best advice is to preserver through nonconstructive critizism (ie. people who critizise you as a person rather than the comic itself) and try to do different things. Push yourself, read up on various other comics to gain hints or techniques, and overall find what you want to express in your comics and try to convey it in the best way possible.
I hope this is some help