Nonono, absolutely not gardens! 
You don't want to tech math either and not currency either.
It's very very rare to tech math in iso. Optics beeline is super common.
And thats without GLH! With GLH the enormeous benefits of astro become just ridiculus.
I suggest you go to optics with one additional city, getting the total up to 4. And the spot I suggest is that PH 4N of the piggies since that spot can start to mature loads of cottages that will serve you throughout the game.
Once optics is in, you can settle 2-3 more cities while caravels are cruising toward the AIs and you do alot of tech trading and while you wait for GScientists to bulb astro.
After astro you can REX like a mad dog!
Btw, keep those two forest that capital and third city are sharing, those two are nice since they give health in both cities.

You don't want to tech math either and not currency either.
It's very very rare to tech math in iso. Optics beeline is super common.
And thats without GLH! With GLH the enormeous benefits of astro become just ridiculus.
I suggest you go to optics with one additional city, getting the total up to 4. And the spot I suggest is that PH 4N of the piggies since that spot can start to mature loads of cottages that will serve you throughout the game.
Once optics is in, you can settle 2-3 more cities while caravels are cruising toward the AIs and you do alot of tech trading and while you wait for GScientists to bulb astro.
After astro you can REX like a mad dog!
Btw, keep those two forest that capital and third city are sharing, those two are nice since they give health in both cities.