Take advantage of enemy weaknesses. Soldiers are weak to Fire magic, robotic enemies are weak to Lightning magic. Use the Assess materia, once you obtain it, to identify further enemy weaknesses.
A good tactic is to use your standard attack (the square button) to build up ATB. ATB will let you unleash magic and commands to do heavier damage. Blocking is also a good idea to reduce damage from enemies (press R1 on your controller), and also builds up ATB!
Just as in the original game, you can heal your party members outside of battle using items and magic. This means you don't have to heal as often within battles, allowing you to focus on dealing out damage.
If you learn an ability from a weapon (e.g. Buster Sword), then you can use that ability with ANY weapon. You will need the weapon equipped for a while to build up towards learning the ability...
You can buy the Steal materia from Chadley, for 100 Gil, in Chapter 8 after finishing Battle Intel Report 7. Then equip the materia to a weapon. Using the Steal command will use up one ATB point, and stealing successfully is not guaranteed; it can take many attempts.
N.B. This is not a complete Steal List. It aims to feature only the more significant items you can steal in the FF7 Remake.
Limit Breaks Guide
Enemy Skill Guide
Final Fantasy VII Remake Guide
List of Every FF7 Title
Other FF7 Websites