While I don't disagree with Davio, I think your real mistake was less subtle than lookout vs warehouse.
Your mistake was lookout vs warehouse and Davio was too subtle about it.
If you add the lookout a bit later, after the first couple of minions, you can immediately start playing it frequently. The reduced hand size will not matter very often, because Minion can give you a new hand afterwards. Opening lookout does horrible things to your chances of hitting $5 early.
Your opening buys
need to bring you to $5. That implies Silver/Silver, Warehouse/Silver or Pawn/Silver.
Silver/Silver isn't that hot because Silvers will be less useful in the rest of the game.
Warehouse/Silver can work out great if you draw the warehouse turn 3, but is a bit awkward on reshuffles if you draw it t4. And if you draw a lot of coppers without Silver, you're in bad shape. I would be totally ok with it, but I don't like committing myself to a risky plan early.
So... my plan would be to open Silver/Pawn. The first miss on $5 I get a warehouse, the second miss I get a lookout. $5+ is minion always.
I might add Apprentice, but only after the minions are gone.