Season 7 Skeleton King-Royal Ghost

1st round: Place the hero in the middle of the second row. Generally speaking, you don't play any minis here. Skeleton King can easily win against every other hero in a 1v1, and if you lose anyway, it would not be such a big deal.

2nd round: Place the royal ghost to the hero's left/right (based on where your opponent put his minis in the previous round) and upgrade him with his 3rd ⭐.
You can now either
-place a spear goblin / ice wizard behind the hero/royal ghost;
or
-upgrade the royal ghost one more time with his 1st ⭐.
(You can do both if you lost the first round. If you won, I suggest you the first option instead. The goal is to separate the enemy's frontline, which will chase your goblin/wizard, ending up being vulnerable to the isolate ability)

3rd round: max out your royal ghost.

4th round: based on your opponent's minis placement and team, you can play a prince to counter silly minis such as mini pekka (if she has the dissipate ability which bothers our hero) or ice wizard (if you are able to send your prince to the other side of the board. Consider using his 2nd ⭐ to prevent self stunning)

5th round: you can upgrade the remaining units as you like. I usually get 1st and 2nd ice wizard's⭐ and Prince's 3rd ⭐ which is always nice

//////
Mini pekka is a situational unit, basically for her dissipate ability which may come in handy. But I still don't use her that much.