Ocean's Embrace is a good ring, however it's only 100 Defense. You're going to have a severe lack of defensive stats due to not using enchants, so it really won't compensate enough.
Typically you'll use Solid Thor Leather Belt, Ghostly Ring, Ocean's Embrace, Warrior's Courage Emblem, and a Nose Ring. It's cost effective and offers balanced set of stats for a relatively low cost. The alternative is dropping the Ghostly Ring and Thor Leather Belt and using a second Ocean's Embrace and a Evil Monster's Leather Belt.
http://vindictusdb.com/item-comparer?i=ring_ghost_thank:belt_thor:earring_sargamu:ring_blue:charm_courage_warrior;earring_sargamu:ring_blue:ring_blue:belt_linotoss:charm_courage_warrior
I'd go with the 2 part Dreamwalker set bonus anyways, as it's good if you're using a Dreamwalker Twin Sword. Even if you're using the Twin Saber, it's still pretty effective.
Raider's is a really "all in" set up. It's not very viable in a party where you have to take into account lag, unpredictable AI, and other people. In theory it's the best if you can expect perfect playing, but that's really really hard to pull of. It's also not a big enough boost to your attack unless you enchant it. But in a +5 no enchant set up, it doesn't boost your stats by enough to make it worth it.
With enchants, you could throw on Well Balanced and Force onto all the parts and then you're looking at a ton of Attack Speed, Balance, and 500 attack instead: but this is with enchants. Without them the Raider's set is largely outclassed.
However, if you just have to use the Raider's set, I could suggest having two sets. It's not uncommon for some players to own two sets, and while it's very costly to own two double enchanted sets: it'd only be about a 20m investment for you to own two +5 sets. If you're not having too much trouble staying alive with your old Passionate set, you should be okay to run around with a Raider's/Apocryphal.
It's still 1.1k Defense for only about 60-70 Attack. So I'm not a huge fan of that trade off. For efficiency, it's still best to run the BH/Apocryphal mix. The Raider's/Apocryphal will work: but it's just not as good.
Edit: Oh right, and since this is for Lann. Agility is still very important, BH/Apocryphal has a gigantic (~70) Agility advantage over Raider's/Apocryphal.
I'm also ignoring the Swift mixes largely due to the fact that it's more effective to sink money into a set you can use for a while rather than a set that will only last you 5 levels. Swift pieces are fairly expensive, so just waiting to get the Apocryphal parts is more effective.