1. When you load into a game make sure you have Recuitment Centers built. If you don't have them you will not produce any new troops.
2. When taking a new territory make sure you have at least 7 troops on the province until the moral goes up at day change. That will prevent the province from revolting and any troops on there going to another country.
3. Keep an eye on your resources. If any of them drop to 0 you're going to start losing moral and troops [if it's food you have 0 of] and your provinces will start revolting.
4. Teaming up with your neighbors can reduce troop loss when attacking countries together. Communication with your allies is super important.
5. Level 2+ forts hide troop counts and helps tremendously in defending your land from attacks.
6. Build advanced units as soon as possible. Cars and Calvary are useful before anyone has artillery and can give you a leg up on players just using infantry.
7. Railroads, Harbors, and Factories all increase the production of the resource that territory produces. Railroads also increase the speed of troops moving across that territory and Harbors decrease the embarking/disembarking time of troops.
8. Leave the small AI nations alone at the start of the game. You can use them as buffer nations, and force others to either attack them or move around them to get to you. You can also give the small AI nations Right of Way making your relations improve even to the point where they give you Right of Way.
If you have any other tips to share with new players please comment them down below! These are pretty basic tips, but I'm surprised at the amount of players that don't know this information. Hopefully this helps some people Also please correct me if I got anything wrong!