New to GTA Online, need some advice.

Been playing GTA Online for about a week now. Got up to level 29 mainly by doing all missions solo, robbing stores, selling cars, etc. I have about $200k in the bank, and have a shitty apartment with a 2 car garage. Haven't bought a car yet; I'm still using my first stolen piece of shit and the free Elegy. Should I get a badass car first or a high end apartment? I think I'll be at $500k by this weekend. Also, I've been holding off on joining heists or any kind of group efforts until I'm confident enough that I won't be a burdon. Is that the right thing to do or should I just say fuck it and start doing some group missions and heists?

Thanks!