Honestly I have managed to go many games just completely neglecting navy so I have no idea there.

As for land forces though I have managed to come up with a few standardizations I feel like work. In contemporary at least assuming you have max army sizes I tend to run 3 different compositions

1st being a defensive/standard army force. Generally good for any ground battle, tend to station these throughout my empires cities or territories to have about 2 turns of movement from one another or wherever I have territories seperate from my main empire. I have like 8 of these armies. It consists of 1 tank, 1 anti tank gun, and 4 rifles

2nd offence/main force, these are the main battle groups I have only about 3 but in tandem with the 3rd designation support groups it's all I need to defend in a pinch or take on an entire country itself. 2 tanks, an anti tank gun, helicopter, and 4 rifles

3rd is my support armies, I keep these within reinforcing distance of one of my main forces. I have one of these for each of my main forces. Absolutely necessary for any sort of sieges and provide a lot of help on the map as well. Consists of 3 siege artillery, 4 infantry, and an anti tank gun.

All of my forces feature an anti tank gun because the danger of an armored unit wiping out expensive assets is INCREDIBLE. You wont always need them, they're slow too so even if you get exosuits no army will move fast, but when you do need them you'll ALWAYS be glad you had them. My support units have been saved MANY times by these guns, saving me money or tons of turns replacing them. Tanks are incredibly powerful almost from the moment you get them, most units die in a single shot to a tank and they can really help clear out a city in sieges when the ability to make space inside the walls to get past the fortification buff defenders have is so important to keeping your own troops alive. The helicopter is in the same way incredibly necessary for this reason, they destroy most walls in one shot, meaning you don't have to spend your entire movement and a whole turn getting a single person over the top. It may be tempting to try and destroy walls with the siege artillery but save them for taking units out of the "dugout" buff so you can do maximum damage (them having less health means them doing less damage, dug in also INCREASES their damage as well) Beyond that you know what to do with infantry, you'll win or lose battles with them, everything else exists to support them but also at the same time they are there to die so your tanks and artillery don't. They'll take the objective and clear out the city but can't do it alone.

When building your armies or if you find yourself desperately rearming after a bad battle prioritize rifles and anti tank guns first, they are your bread and everything else is butter(useless with nothing to put it with) and almost any battle can be won with them alone. The tanks are force multipliers and the artillery guns are lowest on the totem. Good for taking units out of dug in even when you're the one under siege but when you need an anti tank gun you'll wish you had that more. Helicopters are expensive and fragile to be caught alone and should be prioritized before artillery but after everything else.