a few basic things that might help you if you're new to the game:

use your infiltrator or an agent equiped with cloaking tech, proxy hacker and a silenced weapon to scout out the base, disable cameras and security, then move in with your squad and get into a good defensive position. from there you can either lure the guards into an ambush and ff them down one by one or continue with your infiltrator to the next section. if you roll in and shoot at everything including the cameras you will trigger a lot of QRFs which will get you killed unless you are very good at the game. whenever you see an exclamation mark above an enemy, close the gap with your soldier and melee them (unless it's a drone in which case you simply ff it down).

use your support to slow down time whenever you are in a tough spot. use your soldier to lob grenades at enemy squads and to spawn ammo for the team, and your hacker to take over enemy heavies or commanders. send the commanders back for cloning when you don't need them anymore. commanders are the best clones in the game so try to only use commanders to clone your agents. always ff your opponents starting with the squishy guards/drones.

as for money, focus on hitting the major banks and siphoning all the ATMs in all four sectors before you go after other missions. this will get you the shinies from the black market and make the game much easier.