1. Human form only is feasible on WSs and PBs. Some view it as heavily gimping the character but I absolutely love my Human only PB. However, early levels will be a big pain in the butt and so you may want to do Human/Nova until ~25 and then respec to Human only.
2. Depends on what you want to do with the character. Pick an aspect of two you want to excel in and build around it.
3. Eclipse is full of awesome. Perma even more so but by no means required.
Be sure to read the Kheld guides, starting here.
Ok. The low levels are no problem as I am already lvl 37. This character was shelved for a while and am dusting her off and am going to devote my time/inf to her now.
OK, the 'making' in the title threw me off and I thought you were starting from scratch.
I woud definitely pick up the Gravity Shield and Twilight Shield as they cover your most common damage types. Stygian Circle is a must for healing and recovering endurance. Shadow Cloak and Superspeed will keep you pretty much invisible and you pick up a +Perception. Eclipse has already been covered.
On the other side: Sunless Mire for the buffs and debuffs plus a bit of the damage it puts out. Gravity Well is a Mag 3 Stun and very handy to make things not shoot/kick/whatever at you. Gravitic Emanation is a Mag3 Stun. Shadow Bolt and Ebon Eye both recharge pretty quickly and either should work out well. Add in Shadow Blast to keep hitting things from a distance. Dark Extraction is a quick way to be a one person team.
Additional Power Pools are up to you. On my PB I went with Fitness for the Stamina. But if you can slot decently and build with some +recharge with IOs then you might be able to keep Stygian Circle running enough to keep yourself filled.
YMMV and remember I currently have all of one WS so far but I am sure some of the more experienced members will chime in.
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My lvl 49 WS has been fun and agree with others here. Human form is definitely do-able. My WS is all human (just recently got the Black Dwarf form at 49 just cause I like the form 
) and works just fine. Granted he's a little slow in solo'ing (mainly cause he has quite a few empty enhancement slots...I'm lazy!) but is great on teams.
I picked up Nebulous Form (I think that's the power's name...the one that gives you phase shift and +jump). I thought I'd like the power because, "hey it's phase so it'd be handy" and I thought the +jump would be considerable to Super Jump or IR....boy was I wrong. The jump is noticeable but it's not a travel power per se....and it takes a good 1-2 seconds to get into the 'phase' portion so...uh...yeah...going to respec out of that and get the Gravitic Emanation power (the cone stun) most likely.
I have all 3 single target ranged blasts, Gravity Well (the Mad 3 Hold, not stun ) which is just an awesome power, Unchain Essence, Dark Extraction and the self-heal power. As far as secondary goes, I have almost everything (except Nebulous Form when I respec out of it). I don't have Eclipse perma (would be nice) so I do have all the shields still.
Power pools I have are as follows: Fitness for Stamina of course, Speed for Hasten (no SuperSpeed...I can live with teleport for traveling) and that's it I think.
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I'll try to be nice and polite on this one.
Powers I concider manditory from the primary and secondary.
Sunless Mire (3-5 total slots)
Gravitic Emmanation (2-4 total slots)
Gravity Well (4-5 total slots)
Stygian Circle (4-5 total slots)
Eclipse (4-5 total slots)
Dark Extraction (5-6 total slots)
Unchain Essence (4-5 total slots)
Shadow Cloak (1-2 total slots)
Inky Aspect (1-2 total slots)
*Dark Nova (2-3 slots +12-16 added slots in squid powers)
*Black Dwarf (3-5 slots +12-16 added slots in dwarf powers)
*see comments below
I will grudgingly admit to human only being "viable", but I will also contend (if you have the money to compensate for lack of slots with IO sets) that a Tri-Form will always outperform a mono or dual build WS simply because you will never be without the perfect tool for every situation.
No matter how pimped out a human only shade is they cannot tank (Tank meaning hold agro, not the I can take buttloads of damage and not die while my team is screaming help me type of Tanking), and a squid form will always outdamage the human forms attacks (outside of the 2 nukes) especialy if your building alot of recharge so you have a flawless chain of squid attacks.
That being said if you don't care to tank and don't mind having less damage in your chain of attacks then the forms are not really required.
If you PL'd to 50 just to get an "epic" thinking you'd be �ber, you're going to be sorely disappointed with the HEATs, because the VEATs were designed so that anyone with one good finger and a braincell can rock the toggles.
I am finally making a WS and after playing around on Mids, I see they can become very, very powerful. I have a few questions and would also welcome any tips if you have any.
1. Is a human form only WS feasible? I was thinking of going human/nova or human only.
2. What powers are most important to have slotted if I decide to go human/nova?
3. Is perma-eclipse that awesome? I have the money to do it, just not sure if I want to or not.
I know I am missing alot, but slotting a WS is very overwhelming at times and I am looking for some direction to get me going.