Advice of nurgle with the glotkin nd mostly mortals?
Advise Sylveneth also? donno anything about the army.
Advise on indoneth deepkin also? Dont know much about the army either
Lol I may as well play for you ;D
Burgle are attrition - you have to grind them down (hard to hit, lots of toughness/wounds etc) keep them at range so you don’t get bogged down and watch out for burgling Simmons taking objectives.
Sylvaner are evil

their woods are their key weapon - no line of sight through them, do not charge into/through them as that will cost you models, their units get buffs being close to them and they can summon into them - so yeah fun times

Blast big units of driads at range as they are actually pretty good in combat multiple long range melee attacks with extra buffs etc, hunters are pretty nasty so look to take them out, if they have allarielle she is seriously powerful (mega combat tank that can insta kill and spawn new woods when she does so - also she heals everything constantly) double turns on her are veeery useful - if you commit to combat make sure it’s enough to blast her away in one go else you probably won’t be able to, Dorthu is a combat master and deals lots of damage, dricha is a horde killer (mortal wound pump) all else are meh - but I expect you will see the above.
The sea elves are pretty nasty too, eels are your enemy (don’t let them charge) they gain big buffs for it - the spear ones deal a bunch of mortal wounds on charge and gain melee boosts the others are defenders, kill any big turtles you see as they give armour benefits to lesser folk, their base troops are easy to kill but can hit fairly hard in combat - watch out for the tides changing as one will give them always attack first etc, always kill off any supporting heroes they have as they all give out decent buffs - the big guy with the sea cloak is pretty mean - he can heal and dish out some fair damage - wipe him out and that’s a quarter of the army gone in one blow.
Try and stay away / lure their troops away from ship wrecks as again they give buffs and their sea kings are pretty hardy in combat + give eels/sharks buffs