The easiest achievement to unlock for Operation 3 in Gears 5 is "In The Name Of..."
All you need to do is go to the store (menu button) and craft the Cole, Clayton and Queen Myrrah totems for 100 scraps each.
You don't have to unlock the characters as some guides suggest, just craft 3 new character totems.
I didn't have this option, prob because I've only played the game to get the MS points in the past. I'm still on Gears 2.
For those that haven't played the game much, another easy achievement for the 500 pts is the "Buying Time" achievement.
From the menu choose Escape > Custom > Host Private > Barracks >>>> When you have control, go through the first door on the right, and then look for a control panel which should also be on the right with a green light and a switch. Hit the switch with "X" and the cheevo should pop after a few seconds.