Here's a list that somewhat illustrates where you'll wanna go. It has three detachments: A Combined Arms detachment from the rulebook, a Deathwing Strike Force detachment from the Dark Angels Codex, and a Ravenwing Attack Squad formation.
Ravenwing Command Squad [6x Black Knight, Ravenwing Apothecary, Ravenwing Champion, Ravenwing Grenade Launcher]
This squad has the only models not yet in your collection, but three more Black Knights must be at the top of your shopping list because this is the best unit in the codex.
Interrogator-Chaplain [Auspex]
··Power Armour [(None), Bolt Pistol, Mace of Redemption, Space Marine Bike]
You'll want to convert some of those bikers into
HQ: Interrogator-Chaplain and/or one or two Librarians. While deploying with the Ravenwing Command Squad, they should have an Auspex to deny the enemy cover from the squad's plasma talons. This example Chaplain has THE MACE of Redemption relic, but that's optional; drop it if points are tight. Using a Librarian instead of or in addition to a chaplain is totally fine too, just always make them Mastery Level 2.
Scout Squad [4x Close combat weapon, 4x Scouts]
··Scout Sergeant [Boltgun]
Scout Squad [4x Scouts, 4x Sniper Rifle]
··Scout Sergeant [Boltgun]
Unless you're building a full Battle Company within a Lion's Blade, Tactical Marines are dead. Scouts with bolters are somewhat more versatile than
CCW or snipers, but these scouts will net you maelstrom objectives.
Ravenwing Bike Squad [Plasmagun, 2x Ravenwing Biker]
··Ravenwing Sergeant [Chainsword]
Sure why not.
Company Master
··Terminator Armour [Relic Blade, Storm Bolter]
Deathwing Command Squad [Assault Cannon, Deathwing Apothecary, Deathwing Champion, 5x Deathwing Terminators]
Deathwing Knights [4x Deathwing Knights, Knight Master]
The second detachment, a Deathwing Strike Force. Unfortunately Belial is far too expensive, so you'll always play his model as something like a Company Master. Relic Blades, Storm Shields, and Thunderhammers are all good for him. Deathwing Knights can be pretty good if they can catch your enemy's biggest baddie, but know that terminators will rarely earn their points back in competitive games. Try to position your Ravenwing units at the end of turn 1, turbo-boosting if needed, so your Deathwing can deep strike within 6" of their teleport homers without scattering at the beginning of turn 2.
Ravenwing Attack Squadron
··Ravenwing Bike Squad [2x Meltagun, 2x Ravenwing Biker]
····Ravenwing Sergeant [Bolt Pistol, Melta Bomb]
··Ravenwing Land Speeder [Heavy Bolter, Typhoon Missile Launcher]
The third detachment. This formation's existence enables your Deathwing to arrive on turn 2 without rolling for reserves. Grav guns are also good, but melta is shown here because there's no other ranged anti-tank in this list. If your local group doesn't like three detachments, then just fold these into the Combined Arms detachment.
Get it.
Now, if you keep playing Dark Angels, you'll need to decide which direction you're building towards. Ravenwing is the most competitive option, which means buying one or two Darkshrouds, possibly Sammael, grav gun bikers, and as many Black Knights as you can get. You can mix in a Deathwing Strike Force like the above until you can replace them with bikes. The Ravenwing Support Squad is also a good formation if you get two more Land Speeder Typhoons.
Alternatively, you could build the Lion's Blade full Battle Company. This is a big deal: Eight tactical squads, two assault squads, two devestator squads, and a drop pod, rhino, or razorback for all ten. The bonus is those dedicated transports cost zero points and all overwatch happens at full ballistic skill so you'll nullify assault armies. If you do this, paint all of your dudes as a unique successor chapter (not green) so you can also play them as a Gladius Strike Force from the Space Marine codex (which is probably better anyway.)
Hope this helps!