Ok, so we'll start with the simplest building block of a Battle-forged army - a Combined Arms Detachment (shown on page 122 of the rulebook):
We'll take Ezekiel as the
HQ, as he adds more than Balthasar in terms of increasing the effectiveness of other units (the downside is he doesn't have an invulnerable save).
To round out the Troops sections, we'll split the tactical marines into two units (equipping them as per the Dark Vengeance models, which is presumably what you have? Plasma pistols are a bit of a
YMMV weapon, but we'll leave it in for now), and take the sniper scouts (who we'll also give camo-cloaks to, to increase their survivability).
Keeping the
DV models as-is, we add in the Ravenwing and Deathwing. Then we're left with the quandary of what to do with the Vets:
Because Dark Angels don't get access to Sternguard, quite often you'll see a Company Vets or Command Squads equipped with Meltaguns and stuck into a Drop Pod to act as a suicide tank-killing unit. This isn't cheap, and dependent on your opponent bringing a worthy target. The other option is to give them a few melee toys and stick Ezekiel with them in order to blender things in melee (we'll also add two Storm Shields to "disposable" models, so that we can place them at the front of the unit to soak AP2-3 firepower). If you've got the parts for an Apothecary, we could use this unit as a Command Squad for extra survivability.
So that thought process churns out:
Ezekiel,
Tactical Squad (8), Plasma gun, Sergeant with Plasma Pistol.
Tactical Squad (5), Plasma Cannon.
Scout Squad (5), 5x Sniper Rifles, Camo-cloaks.
Deathwing Terminators (5), Assault Cannon, 1x Chainfist.
Company Veterans Squad (5), 2x Storm Shield, 2x Power Weapon.
Ravenwing Bike Squad (3), 1x Plasma gun.
All that brings us out just shy of 900pts and ideally what we'd use to get it up to 1k is a pair of transports (for the Vets and larger
Tac squad). Aside from a single game type (Purge the Alien),
40k is based around capturing and holding objectives, and transports make slower units like tactical squads able to get where they need to be quicker (also gets them into rapid-fire range quicker, so you can start killing stuff

).