I wish we ere in the same room and had half an hour to rave about gobbos.
I have run a Night Goblin army since the start of 7th ed, winning and placing at numerous tourneys and winning 4 out of 7 games at Adepticon last year with an Australian tourney composition restricted army vs 'anything goes' US armies.
Far and away the biggest weakness is animosity because invariably no roll helps, unlike orcs you almost never want to get into combat.
I take by 'all gobbo' you mean no orcs, and that is how I roll, any more restriictions and you really are needlessly crippling your force.
ALWAYS take a regular gobbo general or Skarsnik for Ld8.
ALWAYS take a
BSB with the standard of discipline to give your general Ld9
Mangler Squigs are awesome if only to frustrate and distract your opponent
I have had immense success with 2 giants running down 1 flank, almost always they will both make it into combat, Ld10 stubborn and terror means they can run free wherever they want
I am about to work on my first arachnarok spider so cannot say how well they go.
Gobbo chariots are great if for no other reason than they make great redirecters and can really sting when 2 or more get a charge.
Run
NG units in depth, a unit in horde formation out the front, then the rest of the
NG units behind. The enemy lt unit runs forward and only 1 units fanatics are released.
A snotling pump wagon sucks, Make it
St 5 and
4d6 mvt and times by 4 and you have the most awesome flanking force in the game - 8
d6 St 5 hits and then the (crappy) snotlings get to attack.
The artillery is fantastic - doom divers are only pipped by upgraded dwarven artillery for effectiveness, but are much cheaper.
At my games club we call my massive unit of squigs 'the lawnmower' because they lay down a hell of alot of hurt. Also ITP.
I really struggle with the squig hoppers thanks to the rules for skirmishers with random movement (check it out, it sucks for larger units) and that they are cav makes any 2nd rank useless, however they are ITP and do not suffer from animosit making the unit with the most unreliable movement the only unit guaranteed to not do something you don't want them to do.
I prefer wolf riders over spider riders as they are cheaper in smaller units, but forest strider can certainly help on the spiders.
Here are the 3 gobbo armies from the 3000 point adepticon tourney.
My favorite to play is the cav army (and yes, that is a unit of 40 wolf riders), the most effective the one with the mass of artillery, mine has the giants.