Don't bother with the staff (they ruin any cars you try to sell and thus your income from the legitimate side of the business) or the cosmetic enhancements.
I would totally buy the AutoShop now and spend a lot of time doing contracts. The AutoShop on the other hand has the contracts, that although active are a lot of fun and can be quite profitable this week due to the 2x payment. you will still have to make sales on those businesses, so in the end you will need a private session with friends to make quick sales of those businesses every once in a while or you will find yourself much too active doing solo sales. It will not generate passive income but through the Master Control Terminal expansion it will let you source those businesses from a central location, while the Nightclub generates passive income from owning those businesses even if you don't source them.
The Arcade will be needed for the passive income strategy once you own: the nightclub, a Motorcycle Club (MC), a CEO warehouse, a bunker, and cocaine, meth and cash printing businesses. The arcade produces some but it is so little that it doesn't matter. Neither arcade nor autoshop give you decent passive income.
