@Tim: I said "50%" off hand, because pikers get a 50% defense bonus against ellies/etc. I GUESS that means you need about 50% more ellies than usual, but I haven't done a careful analysis. Maybe if they also have walls and/or rivers/hills, etc, the probabilities do change so much that the damage to EC goes over 50%. Anyway, we agree pikers are bad news!
@MG: Agreed (mostly). If the AI is very hostile, you can usually bring them up to neutral by agreeing to all they ask. Though I'm not sure this is wise, and you may do OK even without agreeing. Once at neutral, they are usually willing to trade techs, and this will also raise their attitude, but probably slower than gifts would. I make tech gifts much more often than tech trades. They are often willing to trade maps at "cordial", and are always willing at "worshipful" (if both sides have mapmaking).
Sometimes they cut off talks in the middle. I think this happens mostly when trading techs [or demanding tribute], and not when you are giving techs or attempting map trades. But I'm not 100% sure about the rule on this.
@Paul: About your original question, see the GOTM71 spoiler (my game and Grigor's comments), in which a 1000BC departure is considered a very late start! But that game is Prince/small map, which is not typical.
In my games, I rarely build any horsemen, because I rely on Marco for map info. I don't even research that tech until I am eager for Polytheism (I usually go for Trade first). IMO it's not bad to make a few horses for hut-popping, defense, or even scouting, but I definitely would not build more than 4 or 5. Wait and make elephants, dips, or even explorers.
I usually rely on just a warrior or two (more at Deity level, since they are also useful as militia), or even on my settlers, for early short-range scouting. Or if a hut produces a unit, I use that. Some strong players value scouting and early AI contact more than I do. For me, it depends a lot on whether I expect to find a hut easily (am I on a small island? or a large land mass with rivers? ).
IMO almost nobody makes enough triremes for EC and/or trade (and long range scouting). Before 2000BC you should be making mostly settlers for quick new cities (and maybe 1-2 scouts). After 1500BC, about half your production should be boats and passengers (probably elephants - or maybe settlers to make colonies, dips, vans, etc) and vans for Wonders. The other half can be more settlers for nearby cities - if you value growth, as I do. The proportions are partly a matter of taste, but could also depend on whether you expect a long game (eg Deity/Emp/Large map; see GOTM70) or a short one (see GOTM71). Longer games call for more growth IMO.
It also seems to be a matter of taste whether to include trade in your EC games. IMO it's useful on large maps (better bonuses, more need for funds + techs), but it's not needed on small maps at easy levels.