Warning: Do not take what Gizmo says to be the unquestionable truth. Gizmo no expert.
I must also say that there's no such thing as good build order. There are so many different possible situations that a build order would be so specific that it would rarely apply. That said, so as to not incure the wrath of TGE, here's my take on things.
If you want to hurt him bad (and he's kinda new) then a mongol raid/boom will likely give you the head start you want. Here's the generic idea
Get Science first and fill farms/wood in first city.
Get Civics before Commerce and plop down 2nd city towards where opponent lives
Get commerce, start trading and taxing
Get Military upgrade
Age advance
Get Military upgrade
Plop down 2 stables and use those free horsies (set on raid) to waypoint throughout enemies countryside. While this isn't the best "build order" to pull of this raid it'll give you the chance to then improve your economy and every now and then check on your horse archers. If they get hurt, attrition or light cav, then run them back and garrison them for a sec.
Here you can chose to keep up the attack, and likely have the battle end before industrial, or just do minor harassment to maintain the edge until better toys become available. Cautions however, if you see your oponent choosing mongols he's likely doing the same. If you see japs,aztecs, beware the heavy inf rush.
Okay, that's all in Gizmo's brain right now, back to work