Ok basically I am interested in making a ganky thief that can help a group seal kills.

Not really all that interested in stealing other than as a prep denial tactic.

I have a few questions about skills I tried a search but either it is not working or I don't know how to use it. (or the info isn't there.)

I haven't played much in the way of melee before, and would not really call my self an extremely skilled player. I know a decent number of high level trap and poison ingrediants (cataloged while searching for wands).

1. Does weapon trip work on flyers (if so is there another way it can be avoided, does the weapon used have a big effect on its effectiveness). Is success rate and lag similair to trip, will cheapshot fire on it?

2. Isolation/separate. Advantages of one vs. the other, can either be used on people already in combat?

3. Anyone have experience with parting block, how often does it fire?

4. How do the four knockouts compare (weapon butt, blackjack, inhaled, garrote) in terms of success rate and restrictions on when you can use them.

5. Any must have skills for group combat with a thief.

trying to decide between two basic options
1. Poisoner with plant and weapon trip, cheapshot, precision strike, and a few filler skills (8 points left, 18 if edged)

2. Going thug up to parting block then not sure.

I like character building (it gives me something to look forward and focus on during the boring play times so any advice on how to procede with a decent thief build would be appreciated).

The prime concerns are being able to survive and or escape in group combat, and to seal kills in group combat. I don't plan on doing a whole lot of solo honorable combat vs. warriors and such.