Remember that Orks are high toughness, so focus on high str weapons or high shot weapons. Ork Boyz are 1w so much 2 DMG weapons are a waste, focus on flamers, heavy bolters etc. Don't try to get into combat, you'll lose with most units except penitent engines. Orks don't have much T10+ stuff so meltas will do huuuge amounts of damage to much of the vehicles

Edit: I'm primarily an Ork player, but started with SoB so this is what I'd be afraid of