How i screwed up mass effect 2

For the first part, the ship, you need to get pretty much all the upgrades that don't work in game. That means upgraded shields, hull plating, and cannons. If you don't, people die. I bought everything for my ship outside of the medical bay expansion or probe enhancements. Weapons/armor upgrades don't matter, but they're definitely suggested.

For choosing team members for the missions in the Collector ship, I chose Legion to do the hacking, Garrus to lead the second squad, Jack to hold the biotic barrier, Jacob to lead the diversion, and Garrus to lead the survivors back to the ship. I'm guessing Legion can be substituted with Tali, Garrus with Jacob, and Jack with Samura. Don't forget to give the inspirational speech, too.

Generally, my squad through the entire game was Miranda and Jack. Miranda is pretty useful in most situations and Jack has kickass biotic powers. The shockwave move is so incredibly useful for killing Husks. It's saved my life more times than I can count.

Bring the rocket launcher, I'd suggest. It's a good heavy weapon for dealing with those shockwave firing husk thingies and what not.