Tap all lands you control: Add a charge counter to ~. Use this ability only once per turn.
The problem is that this ability can be played even if your lands are already tapped.
Actually that was on purpose. Generating mana means it has to come from somewhere. Is there no way to make this card balanced?
You could have the ability only playable at sorcery speed and/or require the charge ability to tap the artifact, limiting the mana production to sane levels. What you'd likely end up with would be a really good storage land. It doesn't break the fast mana rule, and it's worse than both Elves and Birds.
ie. it would look something like this:
Improved Jeweled Amulet
1
Artifact
T, tap all lands you control: Add a charge counter to ~this~
Remove X counters: Add X to your mana pool
So no mana no the turn it's played, but usable mana production later on. It sucks as an early accelerant, but that's not really a surprise. Working within the constraints of a 1 mana 1-2 accelerant, then how about:
Mind-channeller Ring
1
Artifact
As an additional cost to play Flawed Mox, discard a card from your hand.
T: add 1 to your mana pool
It's a sucky Sol Ring knockoff, but it might well wind up as fair, especially as this is worse than both Elves and Birds on every turn except the one on which it is played.
Alternatively for 0 mana, we could do:
Flawed Mox
0
Artifact
As an additional cost to play Flawed Mox, discard a card from your hand.
Flawed Mox comes into play tapped
T: Add 1 mana to your mana pool.
It's messy but in terms of power this is IMO worse than Chrome Mox and Mox Diamond.