A pile of Duskblade questions, plus seeking advice for spell selection

[Extra Anchovies]

Specifically, single-classed Human Duskblade 20, unless there's a one-level dip along the way that I should consider. I'm unsure if I want to toss in one level of warblade in there somewhere, or maybe something else with good BAB and nice dipping potential. Plan is to have a dragon familiar, and rely a lot on Knowledge Devotion and Arcane Strike. I've got most of it fairly solidified already, but I would like any advice you guys have as far as spell selection goes. I also have a few questions about how some of the feats I plan to take function in various situations.
Arcane Disciple and Arcane Strike at 1st level, Knowledge Devotion at 3rd, Versatile Spellcaster at 6th. I know for sure I'll be taking these feats, although I do have questions about one or two of them which will be presented below.

Obtain Familiar at 9th, Dragon Familiar at 12th. Familiar will be a houseruled-in Gem Dragon (I already have the DM's permission to do this), either Topaz (equivalent to Silver) if I've taken only Duskblade to that point or Emerald (equivalent to Bronze) if I've taken a 1-level dip. Why? The alternate movement modes are great (fly, burrow, and swim), and Emerald and Topaz wyrmlings both have Int 14. That means they have 8 skills, possibly spot, listen, and a pile of knowledge skills to round out Knowledge Devotion. Not sure which of the two types would be more useful, though; Topaz has an extra HD and a slightly better breath weapon (that also deals untyped damage), but Emerald has at-will object reading, which could definitely come in handy.

I'll be sticking with Martial weapons (don't have a spare feat for exotic weapon proficiency). Will probably carry a greatsword and a guisarme.
1. Can I use a familiar's Knowledge skills for Knowledge Devotion? That's part of what drew me to Dragon Familiar in the first place, because I'll probably only have Knowledge (Religion) {I need four ranks for Arcane Disciple anyways, so I might as well max it to use against undead} and maybe one other Knowledge skill. A Topaz or Emerald dragon familiar could have Arcana, Dungeoneering, Nature, and The Planes (the other four that apply to creature types) and have four skills to spare.
2. Knowledge (Local) is described as the skill under which knowledge about humanoids fall. Would ranks in Knowledge Local) apply to any and all humanoids, or would I have to specify a subtype of humanoid to which it would apply? If it works for all humanoids equally, then between me and the dragon I could use Knowledge Devotion against any creature type.
3. Could I use Versatile Spellcaster to re-cast spells gained via Arcane Disciple that I've already cast that day? Arcane Disciple's description says that each day I can cast each domain spell once. Versatile Spellcaster states "You can use two spell slots of the same level to cast a spell you know that is one level higher. For example, a sorcerer with this feat can expend two 2nd-level spell slots to cast any 3rd-level spell he knows." Arcane Disciple allows me to learn the domain's spells as normal for my class, so spells I pick from the chosen domain are on my spells known list. Unsure if the maximum of 1/day still applies to spells cast via Versatile Spellcaster.
Finally, I have no idea what spells I should take and when. I don't really need a comprehensive list, but if you have suggestions for the first one or two spells I should learn at each spell level, that would be greatly appreciated.

ETA: if you're curious about the logic behind the gem dragon familiars, here's an earlier thread in which I proposed a homebrew solution (http://www.giantitp.com/forums/showthread.php?366430-3-5-Gem-Dragon-Familiars).

[Snowbluff]

NO yes no. :smallwink:

[Raezeman]

Before I start, i am not really the best optimiser, but i have experience with the duskblade, so i do think i can give some pointers.

ok, first of all:

The prerequisite of arcane strike is the ability to cast 3th level arcane spells and bab of +4. This means that when going pure duskblade, you can take it as soon as level 9. I do agree that it's a great feat for a duskblade, just don't take it before you are allowed to :p
Also, remember that all spells gained from Arcane disciple depend on Wisdom, not your normal casting stat (INT for duskblade). This the duskblade, who already depends on quiet some stats, depend on one more. Depending on high powered your campaign will be, this might then not be that good of an idea.

Your 3 questions have been answered by previous poster.

About your spells

What i think are what you need the most:
shocking grasp (lv 1) is great to take at level 3 for your channeling, and you'll use it for a long time after that
vampiric touch (lv 3) is nice both damaging and healing yourself.
greater magic weapon (lv 3) is a very good boost. Don't get a magic weapon with more than +1 on attack and damage, put all magic stuff on others like elemental damage or something you like, and use this spell to get the bonus. With a standard duration of hour per level + get a lesser rod of extend and soon you just cast this once per day and you're good. Other weapon wielding party members will also like you for this.

others spells, also nice:
ray of enfeeblement (lv 1) is a good de-buff
bull's strength (lv 2) is a good buff and let you spend the gold for the +STR item on something else
dimension hop (v 2) is an easy way to escape grapple
regroup (lv 3) is an easy way to get your team out of trouble

spells i would stay away from:
direct damaging with reflex halve, like burning hands, chanelled pyro burst, etc. As you will be hitting things with your weapon, you don't really need these, so if you don't get spells with actual saving throws, you have enough with INT 14 (again depending the power level of the campaign.)
exception of the saving throw spells is maybe colour spray at level 1, since as a duskblade if you can bring a foe unconscious, a coup-de-grace from you will hurt.

I'm not that big of a fan of the higher level spells of the duskblade, but:
dimension door (lv 4): being able to teleport a little is never a bad thing
ennervation (lv 4): giving negative levels is nice, and succeeding on the touch attack will probably not be a problem with your bab
disintegrate (lv 5) can do a lot of damage, but it has a fort save for much less damage, so again it depends on the power level of the campaign, but i prefer polar ray (lv 5) for nice ranged damage (though only close range)


Finally, about arcane channeling and your weapon choice. At level 13, you channel your spell through all the attacks of the full round. There have been many discussions around this, but the way i (and my DM) understands this is that even if you then hit the same foe multiple times, it is still only affected by the spell once. So by then you might want to try and hit more than 1 foe with your multiple attacks, making reach your ally. With this, the good old longspear jumps to mind. Also, if you do plan on multiclassing, it is after level 13 that this fits best.