I strongly caution against buying any in-game currency. It's horribly overpriced for a game this age, especially when considering how broken the in-game economy is now. There are plenty of guides that can show you how to get started and build your income without giving R*/T2 a cent beyond the initial price of the game. Check out YouTube GTA channels like The Professional and Tylarious tips on how best to spend your time working for cash.
Be careful on PC. Modding is common and modders can/will break your game, or even put you on R*'s shit list by giving you modded money and items. Always be aware of what's going on in public PC sessions. R* does little to combat rampant modding, but they sure as fuck will not hesitate to screw you over as soon as you affect their potential shark card sales.
That said, there's still nothing out there like GTA Online. For all its short comings and problems, it's still a GTA experience online. Try to find a crew to play with and dedicate some time and you'll find that it's still potentially one of the best experiences this generation.