If you take a look both here
viewtopic.php?f=37&t=24386and here
viewtopic.php?f=37&t=24838You'll see a couple of my Gondor lists, one at 500 pts and another at 1000, both based around an Osgiliath theme.
As of yet I've only properly playtested the army in the first link, but I found it to be a rather capable force, and actually managed to win 3 out of 4 games in a local tournament.
A few things to keep in mind about Gondor lists are:
-Make use of the cheap, affordable heroes
-Stay away from using Knights, unfortunately Gondor cavalry is quite fragile for their points
-You're rather limited when it comes to elite troops, having no access to higher strength value troops
-You do however have heavy armour, especially if you use Guard of the Fountain Court with shields, so though you may struggle to kill some enemies, they should have a tough time breaking through your shields too
-Don't forget to send your rangers into the fight! I can't stress enough how valuable their higher fight value than the average soldier has been to me in quite a few situations.
I hope that at least some of those tips help you out and give you something to go on, and don't forget:
"For Gondor!"