Honestly I just have fun getting on and playing with my friends. We usually just fuck around for a bit, like we'll make up challenges for ourselves or we'll just drive around and jump over shit. Seriously, that's what we do. Every once in a while we'll do a mission or race but getting into lobbies is a hassle so we usually just so the other stuff I mentioned before. For hours. I don't really know why we like doing it because just typing this out is making me bored.
Hey I mean if you have fun doing it I get it. I really want to like this game... but the person I play with I also play COD with and they don't have the longest of attention spans... so fucking around in the city doesn't appeal to them as much as it does to me. I just found the game incredibly clunky and the menus sucked ... just little things like if we all walk into a mission beginning area at the same time why not assume we want to play together? And I got sick of dying then spawning in the country... and getting wrecked by dudes with WAY more money than me was annoying.
Again, I wanted to like GTA Online and pushed myself to play it, and maybe with the right group I could have liked it more... but I gave that game way too many chances and it let me down every time.