I had played GC3 before, including the Mercenaries and Crusade DLC's, but gave it up because I didn't enjoy the game pace and play with Crusades. Recently, I downloaded the free version of GC3 Retribution from Epic Games. I hadn't played GC3 for a while, so that's why titled this as "newbie" thoughts.
The biggest change is the slow initial population growth rate of 0.01. This makes population the most valuable resource early in the game. This has several implications:
- When the "event" pops up the lets you choose a crummy pop-1 planet, always choose it. The planet sucks, but it comes loaded with 5 population who will slowly die off unless you ship them off-world through colony ships. If you time it right, you can colonize 4 more planets with this, but even with a little fumbling, you're looking at +3 planets.
- Benevolent/Outreach is the ideological path to choose for at least the first pick, to get the free colony ship. Not for the ship of course, because those are easy to build. But for the 5 pop the ship comes loaded with, that you'll offload on your capital planet before sending the ship off to colonize some world with only 1 guy on it.
- And once you're on Benevolent, you may as well pick the next 2 Outreach picks to get to "Abundant" (+2 population on founding new colonies). That will keep your colonization expansion going.
- And finally, if you can build "Tyron's Destiny" Galactic Wonder, you should do it. For the free 5 pop colony ship of course.
If you play Retribution with the maximizing pop strategy above, you can find yourself with 20+ planets by Turn 50, while the computer players are scraping by with 4 or 5 planets. You can ignore anomalies, resources, technology, money, military. All that doesn't matter because with 20 planets to the computers 4, you can pretty much steamroll them.
Most overpowered now are the Drengin. Not only can they colonize more planets than anyone else with the pop metagame, but with the 2500 BC per conquered planet, they'll be rolling in the money so they can set taxes to 0 by midgame.
Next overpowered races are the ones with fast movement, like Humans, who can just spread out and grab planets.
Unlike previous iterations, a one-population planet can provide meaningful production. How is that? Build a space elevator and starport next to each other and start rolling in gears, anywhere from 5 to 15 depending on tile and adjacency bonuses. Your empire should be able to producing 300-350 ship production a turn in aggregate by turn 50 when your enemies are probably in the < 100 range.
Since there's no real penalty from going "wide", this steam roller just builds on itself.
Grab an alien capital or two (by turn 100 at the latest), and you'll not only see your production explode, but most of the early technologies (Technological Age, and Age of Expansion) you skipped will be researchable in 1 turn.
There's some other changes like the hyperlanes and supply ships, but they are much less impactful than the slow population growth.