I've restarted, any tips?

Frederick the Great , You're not sure which buttons to press, or you're not sure about how to manage the concept?

When you regroup General A into General B, B picks up some of A's rank (health points in combat) and nobility (number of HP healed per turn). If A is described as a trainer (e.g. infantry, artillery, navy), the recipient also gains an extra star in that category (maximum five), which generally translates into damage done to the enemy.

Because Sophia's skills (described in upper right of her profile) are biased towards artillery (more specifically she has certain bonuses when attacking fortresses and enemy troops in cities), you should buy cheap artillery trainers (e.g. Kutaisov, over and over again) and regroup them into her until she's up to five stars in artillery.

I don't have EW right in front of me at the moment, so I'm not going to attempt to instruct you exactly which buttons to press in case I tell you the wrong thing. That would be an unforgivable disaster, because unlike generals, who can be regrouped and repurchased as often as you like (as far as I know), Princesses are gone forever once regrouped; you have to uninstall, wipe and reinstall, then play over from the very beginning to get them back.

Ultimately there are too many princesses to occupy all the active slots & some of them must be either never joined in or regrouped when their usefulness is at an end. There's an argument that anything Sophia can do against enemy troops, Isabela can do just as well while moving faster in the process, BUT Sophia's specialist capabilities as a fort and city smasher can come in handy sometimes, and she should be one of the last princesses you consider regrouping (if at all).