I know you can deliberately miss Garrus in ME1 (netting some extra dialogue in ME2 when you meet him), but on the large scale of things not much changes. But here's the question: can you skip recruiting him in ME2? I'm not sure if you can do Horizon after recruiting three out of four characters in ME2, something like that was mentioned but I never tried.
So, can you have Garrus in your party for the first time in ME3? --- "Oh yeah!" ~ Lucius the Eternal on most things.
You definitely can't skip Garrus. I think the only ones you can skip in ME2 are the DLC ones (Zaeed and Kasumi). --- DF: So why can a Marauder roll but a multiplayer Turian can't? Delta1-9: You are fighting female turian husks. You have reach but they have flexibility.
You will always have Garrus, Jack, Mordin, Miranda, and Jacob. Those 5 cannot be avoided as you will have to complete all of their recruitment missions prior to Horizon. You can then pick at least 3 more of the remaining 7 (Tali, Samarinth, Thane, Grunt, Zaeed, Legion, Kasumi), comprising at least 5 missions after Horizon. You can come into ME3 with pretty much any outcome you desire. How you play things is up to you. 900 is the minimum EMS you can get in ME3 (and it is below the minimum mark in the display). In one playthrough, I came out with 947 EMS, getting a few bonus assets because I chose to save Jack (needed ship armor to do that) so she could become a Phantom later. --- All of the pieces that puzzled their journey are now in position to land.