I had a look at your armory. Since you do not have a proper PvP set yet, you will most probably bump into some tough fights here and there. Looking through the top arena teams may help you with the basics but end of the day, really depends on your play style. Some gem and enchant heavyly on offensive when teamed with healers while some gem more defensively so it's a little hard to answer your query.
Anyway, once you complete your Relentless set with Wrathful offsets, you should have about 1k res and around 31~32k hp compared to your current 833 res and 28k. You may find things a little different.
Perhaps some general ideas may be of help to you.
For enchants, I would suggest,
Head - 50 AP & 20 Crit
Shoulders - 40 AP & 15 Crit
(You could use the WG enchants to replace these 2 above if you need more resilience at the start. Once you have sufficient from gear, you can swap the enchants again)
Cloak - 22 Agi
Chest - 10 Stats (Some prefer 20 resilience but to each his own)
Bracers - 50 AP
Hands - 44 AP
Pants - 75 AP & Crit (If you're having survivability problem, Stam & Agi isn't so bad either)
Boots - 32 AP (Since you're Unholy PvP, you would already have 15% movespeed, if not, Tuskarr then)
Gems:
Just go Str (Red), Str+Crit (Yellow), Str+Stam (Blue).
Until you start arena-ing and finding the best playstyle for you and your partner, these should be enough to help you get started with the basics for BG PvP-ing.
I'm Blood PvP so I normally don't have a problem with 1v1 scenarios regardless of caster or melee. Mark of Blood is OP.
Here's a tip when fighting a non-DK melee... kite.
Chains of Ice is a very powerful tool. Frost Fever plus Death Coils and Pet damage, works wonders.
The trick is getting out of melee range in the first place but you'll need to practice and figure that out yourself. Best way to learn PvP is to practice. There's no better teacher than experience, friend.