Build a strong army
Skirmishes are a key part of Ni no Kuni II, and apart from a few story missions, they're arguably the most optional. That doesn't mean they're not worth engaging in though, as they have the same benefits as optional side quests have, although you can't just jump into battle with some random group of adventurers. You're gonna need a meaty army to deal with all kinds of threats, and we've got some pointers.
In terms of units, you'll need to learn the rock-paper-scissors effect at the top right of the screen when you're in battle. Basically, there are red, blue, and green melee units, all of which are effective against one but weak against the other, and our advice would be to have just two of four units in each battle. Also, it's worth giving each Skirmish a trial run first as well, so you can see which colour units are most prevalent, letting you prepare for that next time you try it (so if you're mostly encountering green units, you can restart the Skirmish with units that are effective against those).
We'd also advise you to get two ranged units to place at the back of your army as well, meaning you advance like a square, with both melee units up front and both ranged at the back. Here you can shield both ranged units effectively while providing two points of attack for melee, also helping keep a wide front to prevent either one being encircled.
You need to bear in mind that the special attacks (again using R2) can be incredibly effective, so make sure you look at each unit and what ability they bring to the table before making them a part of your army. Each ability also costs a certain amount of Might too - the currency used to call for reinforcements and activate abilities - so make sure you've not packed out your crew with expensive units.
Higgledies are more complicated than you might think
A big part of Ni no Kuni II is the Higgledies, who are little colourful creatures that - via a circle on the floor you can activate in battles - allow you to use their special skills. That's all well and good, especially if you have a set of four that have particularly useful skills, whether it be supportive or offensive, but it's worth bearing in mind that these Higgledies all have personalities.
Yes, much like people the Higgledies aren't all the same, and in fact, you'll often find that some are shy, meaning that you can't use them very often in battle if they're overwhelmed by the confident ones. You may then find yourself going from using one a lot in battle to never using them at all if you introduce a new group of Higgledies, so it's worth paying attention to this every time you adjust your setup. One set of Higgledies may be good, but it may not be worth drowning out the others.
Have you got any further tips to add? If so, make sure to add them in the comments below, whether that's making the best out of your Skirmishes or simply becoming the mightiest warrior in the land.