Max on heroes, take lots of sharpshooters, do not bother with armour, except maybe helmets for your captain or champions.
I'd suggest (without calculating):
Captain, mace, longbow and mace or sword
champion mace+ mace or sword
champion mace+ mace or sword
youngblood mace (+mace)
youngblood mace (+mace)
3 Sharpshooters, longbow, mace
2 sharpshooters, longbow, mace
I do not know if this fits into 500 gold, but it is a very hard list (maces are so cheap and dual-wielding is sadly the way to go in mordheim).
If it is over 500 take away one shooter from the bigger unit.
Strategy: Champions are your close combat units, use them to screen the archers. Captain has a very good BS, so he shall shoot too as long as possible. That reduces the risk of losing him early too.
The youngbloods are too weak to fight alone, but they level up very fast. Keep tham a bit back and charge them into a fight with a stunned or prone enemy to finish him off and rake in EXP.
The archers shoot of course, but with mace and their free dagger they are dangerous in CC too.
One advice: NEVER jump down from a building. Skaven heroes might do this, but humans only cripple themselves when they try...