Here's a general little guide I'm throwing together,
it should get you by with doing what you need to do.
You're going to need a few different gear sets, I'm ranking them in order of personal importance:
Enfeebling Skill Set (For when you're trying to land Enfeebles on higher level mobs)
INT Enfeebles Potency Set (Gravity, Bind, Blind, Sleep)
MND Enfeebles Potency Set (Slow, Paralyze, Slience)
Curing Set (For all your healing needs)
Enhancing Set (For keeping yourself and your DD alive easier)
Fast Cast Set (For a speedier haste/refresh cycle, it helps soloing later on too)
Dark Magic Set (For Chainspell Stunning)
HMP Set (For getting MP back faster when resting)
Gear: General:
-All NQ level 51 staffs at least, HQ if you can afford it.
These are sort of your bread and butter.
-I also personally use the level 73 elemental grips.
-Penitent's Rope or Witch Sash (the former is a great piece,
the latter is better but quite expensive)
-Rainbow Cape/Prism Cape or Aslan/Gleeman's Cape (from Einherjar)
Enfeebling Skill: (Note: I include +magic accuracy pieces too when I can, like Morrigan's Cuffs, though you may find pure INT/MND better. It's a touchy subject.)
Enfeebling Torque (Necessary, imo)
Enfeebling Earring (Nice to have, work up to it)
Avocat Pigaches (Also nice to have, they're from a T2 ZNM)
Warlock's Tabard
Duelist's Chapeau
Altruistic Cape (From sea, not the easiest piece to come by, work up to it)
INT Potency:Snow Ring x2 (Diamond if you can't afford, but work up to them)
Phantom Earringx2 or Morion Earringx2
Errant Cuffs
Errant Slops
Errant Body
MND Potency:Aqua Ringx2 (Sapphire if you can't afford)
Communion Earrings are nice here, but very expensive. Worry about them last.
Devotee's Mitts(+1)
Errant Body, Pigaches and Slops again are nice here
Curing Set:You're best stacking MND where you can here. Skill is nice but a lot of MND seems to do better numbers than skill. VIT also comes into play.
Personally I use some +MP Gear and a bunch of +MND and Fast Cast/Haste, skill where it comes on AF/AF2.
Enhancing Set:Enhancing Torque
Augmenting Earring
Warlock's Tights
Duelist's Gloves (Devotee's here work too. They're level 27 and easier to come by than the AF2 gloves.)
Other than that, stack MND wherever you can.
Fast Cast/Haste Set:Warlock's Chapeau
Duelist's Tabard (Goliard Body works too, since we're stacking FC and Haste. Duelist's is better, but it works.)
Swift Belt
Dusk Gloves/Leggings
Loquacious Earring
Dark Magic Set:Dark Torque
Dark Earring
Nashira Body
Lots of INT
Healing MP Set:Errant Body or Warlock's Tabard +1
Beak Necklace +1
HeirIcan'tspellit Belt (If a Duelist's Belt ever comes your way, that instead)
Baron's Slops
Relaxing Earring (Don't even stress about this. After two years I'm still only half way to this ***)
I could spout off gear suggestions all day. What's important is for you to find your 'balance'. Between +skill, +int/mnd, +MP, whatever it is. Every RDM has a different style and list of gear needs based on race, merits, situation, etc. You just have to experiment and find what works for you.
EDIT: (I just realized I forgot about Elemental Magic. ._.)
Like Enfeebling, this is all about balance.
Elemental Magic Skill - Genie Gages, AF2 pants, AF1 head, torque, earring, Etc.
INT - Errant is REALLY nice here, as are Snow Rings Etc.
MAB - Zenith Mitts, Duelist's Boots, Etc.
The higher level the mob, the more skill you're going to need, just like enfeebling. MAB raises the pure damage, INT raises the damage and accuracy. I believe it's something like +10 damage per MAB and +5 per point of INT. Don't quote me on that. XD
Nukes are something I'm still screwing with, my sets seem to change in every situation. >< Sorry I couldn't be of more help on that one.