First and foremost: As a Defender, you should realize that you're not going to match the damage output of the Strikers, even if they aren't optimized. You can certainly build for as much damage as possible within your class, but you're not going to lead the party in takedowns.
With the extra feat you're being given, I recommend picking up proficiency in a superior weapon of some sort. My personal preference for a Warden is the Craghammer, as it's a pretty high-damage weapon (d10), with an uncommonly high Brutal rating (2; at a glance in the Compendium, I only see two other weapons with Brutal 2: Execution Axe and Carrikal), however it appears in the Adventurer's Vault, so while you'd be able to select Weapon Proficiency (Craghammer) since WP is in the PHB, your GM might not want you using craghammers. Speak to him about it. (Similarly, the Guardian's Call weapon enchantment is absolutely the best -- d10 crit while in guardian form, +2 to a NAD while in guardian form -- but it shows up in AV2.)
You need to be mobile on the battlefield, since your mark is a close burst 1; this also means you're going to be taking some OAs. Something like Defensive Mobility is useful for extra AC against OAs; a Minotaur's Heedless Charge ability also helps if you use charge attacks to maneuver (and, of course, if you're playing a Minotaur... which is in PHB3 -- odd, since PHB3 is primarily a psionics book, and Minotaurs don't really strike me as a psionic race).
You're also likely going to be granting combat advantage on a frequent basis as you'll be flanked by enemies. I don't think there's any way to directly combat this with the limited book selection you've got (PHB3 has Eyes In The Back Of Your Head at Paragon tier), so you'll just have to stock up on defenses. Invest in your armor and neck items.
While you have AoE marks as a free action just for being a Warden, your marks aren't especially sticky compared to some others. Warden's secondary roles are Controller and Striker, but if you want to be an effective Defender, IMO, you need to embrace the Controller side of the character. Immobilize, knockdown, forced movement, difficult terrain... these all help to keep enemies close to you and off your allies. (Form of Winter's Herald is God's gift to Wardens, giving you +AC, +resist cold, creating difficult terrain, and granting you access to an AoE immobilize. It's a level 1 daily power, and I wouldn't be surprised to see it still in use on a level 30 Warden.)
Sudden Roots will also help keep enemies close so that you can keep beating on them. When they try to move away, your opportunity attack sets them to a speed of 2; if they're in difficult terrain at the time (see Winter's Herald again), their movement stops right then and there. (If you can get access to Primal Power, Crippling Crush is another excellent feat choice for someone trying to increase his damage; +CON modifier damage to attacks which slow or immobilize, which synergizes with Sudden Roots.)
Your primary goal is to create a Catch-22 for the NPCs: If they attack you, they're going to miss, or the damage isn't going to matter. If they attack anyone but you, violating your mark is going to cause them to miss and you're going to punish them for it (by pulling them closer to you so you can hit them on your turn, or simply hitting them if they're already in range). Wardens get several powers which help along these lines, such as Earthgrasp Strike (PHB2). You knock an enemy prone, and then deal damage when he gets up. He could stay prone if he wanted, but then he'd grant CA to the melee attacks (such as yours) and have a penalty to his attacks. (Earthstrength Wardens also force the target to stay prone for a round.)