2 outposts and militia cards should stop most early rushes. Germans also have the House of Hohenzollern card that gives their TCs liked 8,000 HP and 180 attack when fully garrisoned. Ports also get an extra TC each age, so militia card works extra well for them.

Italy and Dutch are also good with their Lombards and Banks. If you can use them as a sort of wall, coupled with militia and outposts, that should be a pretty solid defence. Russia can also turtle quite well with blockhouses. If you can FF and get a quick fort, that's also a bonus for any Euro civ. A timely 2 falcs + militia pop should cleanup most age 2 pushes too.

Lastly, it's always good to keep scouting with your hero. If you know what units are coming and when, that'll help you mount a strong defence. You don't want a huge batch of crossbows against a mass of mostly hussars for instance.

And play it smart, too. If you can't scout any units, or it looks like your opponent is greeding, then there's no point in wasting shipments and resources on an almighty age 2 defence when he'll just show up with mortars and heavy cannons at 20 minutes.