Welcome to Librarium Online!
So I've never made a 500 point list. The smallest army I've ever designed is 1000 points. Because of this, I have no idea what people take in that size. However, this is what I'm thinking:
Warboss - slugga, choppa, 'eavy armor (rides with trukk boyz)
16 sluggas inc. Nob, 3 rokkits + Powerklaw
8 burnas including mek, 2 burnas + KFF
9 Trukk boyz, burna and armor plates + rokkit on Trukk
Best I can figure is the sluggas and burnas advance forward, soaking up hits with the KFF as best they can. Meanwhile the warboss takes his trukk around terrain and pops up to assault anything they can get their hands on, doing their best to massacre around the enemy lines until the rest of the boyz catch up.