XCOM 2

- Stick through the arduous hump of the Sectoids and Vipers having the run of missions. Past them combat settles down into more straightforward enemies like the Mutons and Advent Soldiers.

- Give your Sharpshooters an extra clip for their rifle and the Killzone Skill. More ammo means more shots.

- New Weapons and armor are now infinite rather than individually-assembled items. Go right for building them when you can. Proving Grounds creations are unique and individually-assembled items though.

- The Guerilla Tactics School should be one of the first things you build on the Avenger. It's how you expand your squad size once soldiers get past certain ranks.

- Stealth is largely useless, despite the game's insistence on it. If you're hitting a heavy facility, blow cover on the first ambush and just fight your way in. Otherwise when you're spotted you'll just be at the center of getting your ass kicked from all sides.

- The exception to this is the Advent Facility missions. Unlike other major missions, the game actually lets you pop down the extraction point instead of forcing you to use an arbitrary one out the back end of nowhere. It's much more viable to sneak in unseen, plant the charges, then pop the extraction volume somewhere close to just leg it.

- Do not build Nanofiber Vests. The basic Advent Troopers disappear very quickly, and you need six corpses to assemble Plated Armor, which is infinitely available for all soldiers rather than a single assembled piece.