What ukrunner said, except for the fact that you can get more then 80 friends. You can't invite new friends once you have 80, but you can accept friendship invites from others all the way up to 140 friends.
Also, quite frankly, if you are waiting to start trading for or producing goods you need once the tech tree says you need them to advance now you are missing the boat. You can see the whole tech tree all the way up to the end of the progressive age: all the technologies, what they give, what they require in terms of other techs, how many forge points it takes to get them, and what they need to be unlocked in terms of gold, supplies, and goods. You should take advantage of this to plan ahead, far ahead. Don't wait to start accumulating the 18 wine needed for militia until you have spent the 14 forge points on militia, start producing or trading for that wine as soon as you have access to any bronze age goods at all. Do the same with all other techs. As soon as you have access to goods from a certain age start producing them quickly (well, I usually just produce the two out of 5 goods of a certain age that I have a goods deposit for, but it's up to you), trade for the goods you aren't producing, and always keep in mind every single technology that requires goods from that age and how many of each good you need to fulfill all those tech requirements.
Upshot is, if you plan way ahead like this, the fact that it takes 2 weeks, or even 2 months sometimes, to get the goods, won't bother you, because by the time you have finally gotten all the prerequisite techs and spent the forge points on the newest tech you will have long since had the goods you need to unlock that tech. There is a nifty guide listing all the gods requirements of the research tree, including totals for each goods for each age, here:
http://forum.us.forgeofempires.com/showthread.php?58-Goods-requirements-of-the-Research-Tree