The basic way to win is to have a tank chain as generally shown in the image. Make 9000 a turn and a build a tank every turn. These reinforce each other and let you win trades. The CPU will waste its time attacking the near by building which can be flipped easily every turn allowing the $1500 infantry to generate so much value via stalling. This works on every map but 2

Use the bridges as choke points and you can build an early infantry to take some buildings faster. The sniper goes over the river to take the neutral building. The helicopter goes over the to take the objective.

You will use a similar strat here. Use your power to kill the anti air and battleship. Make sure your battleship is not in range of other targets as it gets mind controlled every time for 3 turns. Move your helicopter by the battleship it wont be in range being things need to be 3 away to get hit. Then take the lab. If you did it right you win the turn the reinforcements come

The same strats to win most maps will still apply. Tanks are still king however you need to account for how the AI plays. They AI fears indirect. You will want a few turns of tanks to make a protective front line, and then you will want to buy 2-3 Artillery and Rockets total. The AI basically refuses to go in a tile with multi hits from these in-directs. you slowly inch forward to get enough money per turn to grind out a win with better attacks. Infantry make for great shields and bait as well

Repairing units i have found is pretty effective as well. Units tend to be ineffective once they get below ~7Hp. Infantry usually don't need to be healed as they can take any neutral building at any HP. Medics are overpriced so if you are going to heal a unit walk to the nearest base.

The last thing to consider is the power you are against: AoE, DoT, or Status affects. Most of the time you want to death ball your units, and you can do that vs AoE or Status affects, but Dot tends to get to much value when you do this so make 2 "squads" that are spaced a part so you can still strike. In-directs are much worse to build here if you need units to protect them. You would need terrain. The other option is a bait location that holds more units value than your army. AoE damage hurts but i have been able to just take the damage and push or reposition. Remember they need charge to use their power, so if you can do a lot of damage the returned power might be the only damage you take. Especially, if you over charge their power. Overcharging for those that do not know is doing damage which gives charge to the enemy CO while they are at max charge, and therefore they get no charge. The same strategy works for status affects.

When fighting the mind control power its best to spam cheap units. Strong units will be the target and you will take to much damage. You can bait the power by putting an expensive unit out of range of all of your units but then you are down ~20k which is pretty bad.

The last two fights on the first map, i have not retested myself. A friend of mine was able to do the helicopter cheese on the penultimate fight on the first map. The last stand i have not tested, as that map is long, grindy, and overall unfun. I have done every other level on the first map, and then did one mission on the backside of the map. These have been fairly effective strats.

The last general tip i can provide is sometimes building a single sniper is all you need turn one. As some missions will have a single bridge and a sniper covering that spot is enough to prevent the AI from moving over there, which is very cost effective.