MHF2 and MHP2G (PSP)

[Sforza]

where can i find springnight carps?

From the upgradable fishing pier in pokke farm.

Q: Fastest way to get rubies...?

From normal Rathian:

4% reward for breaking head
2% carve from tail
3% reward for capture
2% from shiny drop

From gold Rathian:

4% reward for breaking head
5% carve from tail
7% reward for capture
4% from shiny drop

From normal Rathalos:

4% reward for breaking head
2% carve from tail
2% reward for capture
5% from shiny drop

From silver Rathalos:

4% reward for breaking head
5% carve from tail
7% reward for capture
4% from shiny drop

I'd pick the normal versions since they're much easier to kill and tail cut. Up to you.