Soul Hackers 2

150 sounds like a lot, but it will come sooner than you expect. After each story dungeon, a trip to COMP Smith is usually a good idea, as you can get attack upgrades, allow yourself to equip stronger Mistiques and learn special skills per character (+ Commander Skills and Demon related upgrades on Ringo). 150 is not all of them, I still had a number of the mistique affinity upgrades/unlocks left by the time I had this. If you are missing some and don't feel like anything else is useful, just spam cheap low level affinity upgrades until you hit the amount you were missing from the 150. You will have access to everything possible once you head back to the Axis after the events following the West Shipping District

Certain upgrades are required for other achievements. For instance, you have to buy every Commander Skill to use them for Battle-scarred Commander. There are some I can also strongly recommend.

Ringo's Surveillance Scan for a chance (or guarantee at Master Rank) to auto analyze every weakness for every enemy you fight except bosses

Milady's Piercer, which is Almighty version of her regular attack but unlike Physical, nothing resists Almighty. Also Harvest, which steals MP whenever she does damage.

Arrow's Vigilance and Capote, which reduce (or remove) the chance to be ambushed and buff Gun Skills.

Saizo's Duplicator and Chandler, for chance to double or triple hit with attacks and have enemies lose one turn if they get hit with Gunfire.