Start a character and grind your way to absolute dominance in Scrims.io.
If you've played isometric RPGs like Diablo or Torchlight, then you'll feel right at home in Scrims. You run around, clicking on anything that moves, and earning XP and gold in the process.
Take that gold back to the start in order to upgrade your character's armor, weapon, and consumables.
You only have one life, so if you're worried you're going to get in over your head, flee. Be sure to upgrade your stuff often, and use the ports to go to higher (and more dangerous) levels.