I'm wondering what the key abilities (if any) are in each. The must-haves, and why. Since it will be a little while before I can just learn everything, so I am trying to plan out what to aim for first.

It will also help me to figure out how combat, you know, goes. For my brand of bard.

I'm pretty much clueless about shadowbeat and ecology but for acrobatics, you want Somersault and Contortion

Looking at the skill lists and asking people on clans, I'd go with:

For bashing
Master or Shadowlight or Spiderlegs in Shadowbeat- mana regen/writhing never hurts, but all your need is master imo
Contort in Acrobatics
Softcharm in Ecology? (not sure if anything is useful besides the charms for dmp)
The abilities in some of the common skills are more important at this point actually.
Once you have those, put lessons into music so your minorsecond is higher and get a maestro instrument if you dont already have one.

For combat, you probably need at least tritrans to be good.
Unless you are trying to kill someone with damage, the only other realiable kill method for HB I know is pfifth/herbbane/bardoon one, with acrobatics for dodging so you aren't destroyed.

My $0.02.

Lets assume a bit more to spend initially. I'm asking here because off-peak there seems to be no one around in the guild. I'm fabled in shadowbeat, master acrobatics and virt in music. I've put a few lessons into a handful of other places, and have about 700 lessons to spend.

Its hard to figure out where to spend them. I may also be persuaded to buy a few more before the conversion bonus ends - if I find there is something really crucial I am missing.

Thanks for the herb bane tip, I'll think about shooting for that if no one else contradicts you.

Does anyone have any information or opinions on:
(and yes, I've looked at the scrying pool)

1. berserk fetish?
2. familiarberserk?
3. transmigrate?

As for Shadowbeat, most of the combative Shadowbeat skills are based off bleeding.

Bloodycaps is the core skill of the skillset, it makes your enemies bleed and you will need that regardless.
Shadowpulse afflicts paralysis to anyone bleeding over 500, hence it working off Bloodycaps.
Shadowrave knocks off balance and Darkheart increases the damage done by any Glom hearing your music (This includes yourself, helpful for bashing).
Nightshadeblues doubles mana loss, this works well with manabarbs as the more mana you lose, the more damage the affliction deals to you.
Wyrdsong passively shields you on Wyrden terrain as long as you can hear the music (helpful for bashing or sparing blacktalon).

You will need to trans the skillset to be anywhere near effective with it, but if you just want most of the good skills while still being able to kill someone, then get to at least Nightshadeblues (around Mythical or so). This will get you most everything useful, while just leaving out Wyrdsong and Dirge.

Of course if the above is too many lessons, then you can just stop at Bloodycaps (around Expert? been too long).

As for Ecology.. I've no idea. Herbbane and Batsbane are really the only combative skills that are must have.

As a Harbinger the only way you are going to kill anyone is with Manabarbs/Egovice and using Minorsixth after afflicting. Ways to keep them from curing the afflictions are Octave and Herbbane. You could also get lucky with Dirge.. but that's about it.

Snakebane + berserkfetish with charybdon a few times is incredibly effective for affliction burst. Other than that, listen to what Daereth wrote. He's been fighting as a Harbinger for quite a while and knows the archtype very well.

Perfectfifth+batbane+dirge

Easiest kill in the game, currently.

Fetishes arn't really that useful as far as I know. I suppose they could be if you found a good way to use them, but you arn't going to trip up anyone even remotely competent afflicting with a fetish 1v1. Might be good group combat potential... but as I said, I don't have experience with it.

Familars are better now than they used to be, they can afflict with poisons which is nice. I've no idea if Familarberserk increases the speed of that or not.

Bleh on Transmigrate, it really just depends on your race.
Deepbonding a bat will get you +1 intel and the ability to Fly (Intel is nice, if you a Faeling you can fly already).
Deepbonding a spider will get you +1 con and the ability to Highjump (Con is nice, you should already be able to Highjump).
Deepbonding a viper will get you +1 dex and something else I'm having trouble remembering. (You don't need the dex)

Autorevival is.. alright. Same spot as your familar, small amount of experience loss.. and a whole bunch of power spent getting a new familar.

Vipe and Widow give poison resistences to whatever poisons they afflict with. One is Mactans and the other is Calcise, I think. Both kind of suck.

Widow is also +1 cha.

If only Widow wasn't female only.. such genderism on this game.

Thanks heaps.

For now I'll aim at herb bane and nightshadeblues.

After that its just a matter of waiting for someone, anyone, to credit-swap with my Aetolian ones.

Yep this is the one I was talking about.