Well I'll tell you right now the lagavulin is going to be very different from what you've tried.
What you've had is mostly sweeter whiskies. Lagavulin is smoky, peaty and somewhat savory. It's something most people either love or hate.
That said, you should try at least one Islay scotch (ardbeg, laphroaig, Lagavulin, Caol ila, Bowmore, etc.)
Glenfarclas and glenfiddich are generally good, affordable sweet whiskies.