King's Bounty: Armored Princess

• If you're playing the Crossworlds version as you probably are, make sure to pick the Orcs on the March campaign from the menu instead of the base Armored Princess one. It's the same overall campaign but with a whole bunch of extra content and overhauled mechanics for orcs and goblins.
• Burn and Poison have been reworked from the previous game to deal percentile damage, changing them from basically useless to one of the best ways to deal damage to large enemy stacks.
• Fast traveling between islands instantly replenishes your Mana (but empties your Rage).
• You get to pick your pet dragon at the start of the game, each of which gives a different passive bonus and starting skill. The blue one (+1 Initiative to Animals/Dragons) is the only one with a really irreplaceable and strong effect, with the caveat that it obviously doesn't do anything without those types. The green one (+1 Intellect, starts with Treasure Searcher) is nice for a Mage in particular since having Treasure Searcher from the start can net you some handy early loot.
• The new Medal system gives gameplay rewards for achieving certain milestones. An important one is the "Grand Strategy" medal which gives +200/500/1000 Leadership for winning 10/30/50 battles with zero casualties, something you should absolutely strive for in the early game where they're significant boosts to your army size. Summoned or revived units don't count, making them highly useful for flawless wins.
• Another good but kind of finicky Medal is the "Trapper" one which requires finishing off 10/50/100 stacks with the Trap spell and as a reward places 1/2/3 free traps on the battlefield and increase trap damage by 25%/50%/100%. This is a very useful effect especially for a Mage, but does requires conscious effort as the traps must land the killing blows to count.
• All classes should consider maxing out the Magic skill "Alchemy" before memorizing too many spells as it halves all learning Mana Crystal costs. Likewise the Mind skill "Neatness" gives more Mana Crystals when destroying items and is worth taking before breaking stuff.
• After clearing a couple of islands, you may get stuck with seemingly everything everywhere being massively stronger than you. When that happens, remember that there are big dwarven lands with reasonable enemies on the other side of that huge bridge in Verona, so that's where you need to push.
• The quest from the Temple of Love (located between Verona and Montero) which requires you to defeat an enemy hero named Hagni on Montero should be done as soon as feasible, as it unlocks the ability to fly on the adventure map. Hagni's relatively tough, but a properly-built Mage for example can defeat her even while she's still classified as "Invincible".
• The exact unit summoned by Adventure Spells used on the adventure map depends on the island you're on, so save first and try different islands if you're hoping to hit some specific unit.
• Demonologists are amongst the best units in the game as they can summon cannon fodder), resurrect troops, and they're even classified as Neutral so they can fit any lineup without penalties. In Orcs of the March, orcish armies (particulary for the Warrior) or a droid-based setup with Engineers, Guard Droids and Repair Droids are also both strong and reliable options.