What is a good Pariden build?

Warlock has longterm advantages, but Summoner gives you the Summon Shadow Warg spell from your first turn.  Given how poor Pariden leaders are at melee, and how many heroes you acquire aren't especially good at this either, it's very, very helpful in the early game.

Again, the choice is yours.  I prefer giving my sovereign L1, and with just a little time out for Exploration and the starting civics in Administration, going directly to Sorcery.  Then you can buy elemental spellbooks.  That way, it's possible to grab several good traits at once, such as Attunement, Natural Leader (lowers cost of heroes, so you can spend that money on spellbooks) Brilliant, and Scholar.  Throw in Clumsy, and you can get a Crown, too, which is invaluable since you'll want to spell up one champion with everything you can find.

Except you're not going to let that sovereign go anywhere near melee, so why not use Clumsy, instead?  Then you don't have to worry as much about the enemy spelling your monarch with Slow when he/she may be the only one with Haste to counter it.

I go for moderate magic strength, as this makes the less magical races more viable.  Again, up to you.

Also, moderate (my choice).  If you're going to do this, consider setting neutral monsters to dense, just to give yourself more of a challenge.

Get Drill.  Adds one to your allowed army size.  Other than that, I'd save those for much latter.  After you get Sorcery, you want to push for buildings that give you more population growth and above all, research (plus Merchant), and you want to go up the Magical tree on the hero branch to get the more experienced ones as soon as possible.  You should be able to pick up enough gear by killing monsters and finding caches, without having to buy much.

A few other thoughts.  Your first hero doesn't need to be a bruiser type to go down the Path of the Assassin or Path of the Warrior.  I typically choose the latter for my first acquired hero, and only choose magical disciplines (such as spellbook advancements) when the other options are relatively unimportant to the build I want.  I save my pioneers for cities, and use arcane monoliths to grab every shard I can find.  If one is positioned near monsters I can't deal with at the time, I try to place the monolith as far away from them as possible.  As my people acquire new spell advancements, I always check for further spells to cast on my melee leader (who has my crown, so no mana cost other than the initial outlay), and good ones to raise research, production, and food for my cities.  Side benefit of monoliths: you can always shop, there.  More spellbooks.  Mounts.  More places to trade in items you don't need.

Best of luck.  Hope that helps.

Interesting, so your Pariden Soverign doesnt melee much? which means no need for flame blade.

Yeah summoner is nice early on but I thinking long term...

I never go for the recruiting/quest techs.. but I suppose they are critical for recruiting champsions? Are quests worth doing?  

How often do you build pioneers? What type of military untis are good ?

Summoner or Warlock.  I'd have to say both, if I went warlock I'd take air or fire (flame dart and storm are at lvl 2) .  Summoner would want some kind of buff spells like stoneskin or flame blade

I'd also take life 1 in there since books you can buy won't teach you that.

Glazunov1 has very valid points.

Yes, recruiting techs are only way to recruit higher level champions (which generally don't suck so bad as level 1 ones that can come with negative traits. )

Pioneers.  I generally build LOTS of them and claim resources and found new towns and try to keep apace of my rivals.  

I make predominantly more mages (Magic tree weapons)  if I have more crystal production than iron (Warfare tree ).

I give it to my chosen champion, who carries my leader's crown.

Thing is, Pariden is such a wimp at melee, that you'll likely to need spellbooks from the start to deal with any battles at all, or Summoner.  You'll otherwise be running away from just about everything except a lone Darkling warrior--and even that might be problematic if it's just your leader and one mage-like hero.  So consider getting more spellbooks and Warlock, or getting just that first Life book and Summoner.  These combinations work well together, though of course others might be viable.  I just haven't tried many.

Definitely for the heroes.  Even when you've acquired a number of levels, it's a real boost to your team to add someone like Soliag the Undefeated.

I build one early in the game. While highlighted, I look at the area my hero's stack has covered, searching for 3/3 spots or better.  I usually go for 5 cities or so, in the end.  Perhaps as many as 7 or 8, but not usually, since this adversely affects the amount of food/growth available to all.

I make my military units, looking at the monk design and editing so that it auto-upgrades on weapon, main armor, etc.  I supply a ring for a few HPs, and some element attacks, and a few traits later on that raise hit points, and level.  I also go for Logistics at some point after getting Drill, so that I can create Group units instead of just Parties.  I don't build a lot at the start, but I do put a couple in each city over time--and might add one or two to hero stacks, to get the experience.  It's also a factor in getting a decent diplomatic response from other channelers, but Pariden's way of getting rid of monsters on your territory is to use spells, so they never even get to your cities.  Which is why have lots of fire shards under your control and at least a couple of heroes with fire spellbooks really help, in my opinion.

My hero stacks are filled out with summons, either from items, or from spells.  Earth is excellent in this respect, though it takes a good while to get to the elemental.  Fire is reasonably good, though ice (water) seems underpowered and surprisingly slow.

Another point to remember is that higher initiative for a given unit in battle may not necessarily be best for your strategy.  You may want a given caster to go first, or a series of casters, or a melee unit that can move far (usually on horseback), cast Haste on itself, then move again to attack at once.  Spellcasting is a bag of tricks, it gives you options.  Several spellcasters in your party provides plenty of options for tailoring combat to your desires.  Set your mages' initiative ratings at points in your battle order where they'll make the biggest difference.

My current Pariden sovereign is

2 Fire Disciple : for flame dart

1 Life Apprentice : you can not pick this up with a book

1 Brilliant :+10% xp, +2/lvl spell mastery

1 Discipline :  for the +1/lvl spell resistance, the accuracy is ok 

1 Scholar: +5 research  helpful at the start

1 Attunement: +2 mana

-1 Clumsy : when triggers it hits a random target next to you (this seams to include other enemies if they are the only option)

1 Warlock : chosen last as professions will let you go to -1 (this was once free)

Playing on a normal large map with default settings.

I have been working my heroes in teams of 1 mage and 1 fighter type with trained units (mainly custom mages)

My sovereign (lvl 12) and her fighter (lvl 11) with only a fire elemental with them have cleaned out two wild lands.

In the warfare tree I got logistics to make my mages more effective and blacksmiths for the extra materials.  Leather armor and spear was my basic melee unit.

Been messing with Pariden lately myself, and my custom sovereign is a warlock, with 2 air, 1 life, 1 earth. It's hard to level now, so the 2 air makes it simpler to get air 4, which is cloud walk, an amazing spell on large maps, where I usually play. The earth book to cast enchanted hammer on your city early (a huge difference in production). That allows you to pump out some units quicker and explore with those to make up for lack of summoning. Air also gives you aura of grace, and if you get life to 2, you can cast aura of vitality to make your troops even nicer. Quite frankly, with this build, the warlock pick is pretty optional, but I like it for later down the road when I fight big things standing in the back (most of my mana is spent on enchant and arcane monolith early). By then I'd also pick up the fire & water books from tech (only after air gets to 4).

Edit... don't know how I forgot this but, impulsive. It's such an op trait.

How does the strategy change with the new beta with essence?

I keep getting owned because i keep concentrating on grabbing shards, improving my default city with spells as essence goes up (concave), building and upgrading outposts until i neglect pioneer building cities

Essence is simply something just about every city should have.  In the current build, it's vital to any city.  I wouldn't suggest building on a square that didn't essence unless you can find the rare 5/2 or 3/5, in which case you've got a town in the first case, and a fortress in the second.  Essence, though, can raise those city stats.  While a building will give you an early essence boost, having it there already simply means that many more spells you can throw to help your cities.

I give the leader's crown to a melee type, who in turn gets all the buffs.

Quests are...idiosyncratic.  I'd leave them alone, for now, though there's one that gives you a nice one-shot item that removes any defect acquired when a champion dies.  Can't recall which one it is, though.  Anybody?

I build a couple of pioneers very early in the game to set up a pair of cities.  Later, I build perhaps three to four more.  Arcane monoliths are the way to go for outposts.  Grab every shard you can find, because they play into Pariden's long suit of magic.  Use your sovereign and champion armies to destroy lairs around any city or outpost thoroughly, and avoid settling near wild areas, since they'll generate wandering monsters until they're completely cleaned out.  Add at least one or two units per city by midgame, and start moving a good, buffed unit into each outpost.