Congratulations on beating Dad!

2 really important points have been made here: 1) after the battle look at unit cost vs how much work they are doing for you_go into the logfiles for the battle and look; 2) save replays_after the battle play it a zillion times and look at what worked and what needs improving-even better, you can look at what Dad did and what Dad did wrong

Papewaio gave you the basic "way things work"; to get better you need to play and Custom Battles work very well for practice.

Have fun!