This is a great topic. If you take the Android Saga on it's own, it seems the 5x boost would work nicely.
But then the Buu Saga boys wouldn't be able to surpass the Base Saiyans even as Super Saiyans.
10x is probably appropriate to deal with all issues. 10x also helps solve the Gotenks, Ssj/SSj3 issue. If Gotenks has a 50x boost for Super Saiyan, then Super Saiyan 3 ends up being a 50x boost as well, if no more.
Which gets extremely crazy. 10x would work best overall for all issues in the manga, and it's what the author pictured it as. Doesn't mean there aren't a ton of issues with it, but it seems to be the best middle ground.
If you intend to go with...
Base Gotenks > Ssj3 Goku ~ Ssj Gotenks > Base Gotenks > Majin Vegeta
Like many would like to do, 10x is the only option that doesn't get extremely out of hand.
Gero's implications are very clear on what Super Saiyan can reasonably be. 50x just would make the humans power far too small for it to matter.
And Super Saiyan should be consistent. So if it's 10x here, it should be 10x on Namek as well.
Does it have issues with Kaioken, sure, but you have to make a choice here, I think the best choice is probably going to be 10x.
Some non-canon material would have issues with it like Movie 5 and 6, but there doesn't seem to be many options.
Ssj2 Goku 100
Base Gotenks 150
Ssj3 Goku 1,000
Ssj Gotenks 1,500
Base Gotenks 2,500
Ssj Gotenks 25,000
This seems far more reasonable than our other options I would imagine.
Also, this approach would boost the humans to really high levels, which seems to be what Gero's implications would indicate. They'd probably be like 50% Freeza level or so by the Androids Saga.
Which makes their struggles against Freeza's force in Super make absolutely no sense, but isn't even Piccolo struggling a bit as well?
