The things I mentioned before aren't a hard requirement, they just allow you to make a lot of money, which allows you to have more fun, since you can afford more 'toys' (figuratively as in cars that don't really have a use and literally as in a toy car with explosives strapped to it). Strictly speaking, you don't have to do anything in online, there is no real end goal, it's really for of a 'have fun' case. Also, after a certain rank (I believe rank 25) you unlock the 5 original heists, these make decent money but also require some setup missions, you can still join other people's heists when you're below level 25. You should also not buy the facility first, since this enables you to do a heist, but the heist is insanely difficult. If you save money you can buy businesses, though these can be rather expesive, it doesn't really matter which businesses you buy first, but you should never by the nightclub first, since this one requires other businesses to make money. The best thing to do when you just start out is grind regular missions and jobs (pauze menu-online-jobs). Those pop-up missions are more like suggestions, that submarine one for instance is more late-game stuff.

How do you play grand theft auto online