A quick guide on how to not get destroyed right away:
Select a grassland patch somewhere on the edge without many players around, many bots and an access to a see/river. More advanced version would be to start in a center and do more diplomacy later.
Send 20% of troops right away when game starts, then move a slider in a bottom left (attach ratio) to 35% and expand every time you get 40% of your population (like 6k, 8k, 10k checkpoints). Avoid PvP.
When there are no more free land left, start conquering bots. Try to encircle them, because you will annex them without spending troops, otherwise just try to get ones located on mountains last, because there's a penalty on mountains. You'll get gold every time you finish out the nation, spend this gold on cities first, then ports and some good forts to defend yourself.
The shift from PvE to PvP must be deliberate and opportunistic. Only attack when you have an advantage like when they're busy with another war, too expanded. Get some allies because breaking an alliance gives a penalty. Don't rush to conquer as it will make you weak in a short term.
Pick a strategy for your mid-game:
City-Maxxing - this strategy involves investing heavily in Cities to achieve an enormous maximum population cap. A player with many cities can field a colossal army, aiming to overwhelm opponents through sheer numbers and a rapid troop regeneration rate. This is a land-centric, brute-force approach.
Trademaxxing - this strategy focuses on building numerous Ports to create a vast trade network. The goal is to generate immense quantities of gold, which is then used to fund a powerful navy and a large nuclear arsenal. This is a sea-centric, wealth-based approach that aims to win through economic and technological superiority.
In the late game build Missile Silos and SAMs in fortified, mountainous locations, break some alliances with a huge attach armies, or break defenses with nukes.
To win launch MIRV on a biggest threat and swarm the area