I've only played 2 and part of 3 but here are some tips. Not super spoilery since they won't make sense out of context

1. Agree with me about Tali/Kasumi being best
2. DO NOT romance Jacob
3. Pink camo space armour is 100% the best thing you can do with your armour customization
4. Sentinel is super good for extra defense if you suck like me