Back in the early 90s at school I discovered warhammer through a friend, we spent all our pocket money on it and time playing and painting, setting up our own school gaming club eventually. I stopped playing in my late teens, money and studies took over, then work and I lost the friends who enjoyed playing over time and sold off the miniatures I owned. Here I am now, a thirty something, each time I play a board game I find myself missing the freedom and dramatic moments of those games, however, my girlfriend of two years is curious about it, and has shown interest!
Sounds like me, though you are younger!
(Quick ban him!!!)
What about something familiar and tropey but also cheap and easy, with the option to expand and get more detailed?
I am currently on a 15mm Conan style thing and you can see some of my game reports HERE which will show you how cheap and quick and easy it can be.