A melee ranger usually goes Strength primary and Dex secondary. (WotC suggested Dex primary and Strength secondary for an archer, but every archer ranger I've ever seen took Wisdom secondary.) As an elf, you'll have a high Wisdom anyway. Your high Dex will mitigate your low AC somewhat, but take hide armor. +1 AC helps. Take any power that lets you retreat when attacked; it's crucial to avoid being attacked in the first place (rather than try to boost your lowish AC).
Your Strength bonus to damage isn't terribly important, because Twin Strike ignores that. You do want every other bonus possible, especially those that "double up". So Lethal Hunter only gives you an average +1 damage at the heroic tier, whereas anything that gives you +1 damage per strike (other than Strength) is worthwhile. Weapon Focus is a good feat, as you don't need to be a fighter to take it (from what I see) and that's +1 damage per sword swing per tier
(basically +2 per round).
Your accuracy will suffer, as elves don't get a bonus to Strength. Invest in an appropriate expertise feat. It's a good thing you're using some sort of sword, as those give you +3 proficiency bonuses. Elven Accuracy is also nice.
