Bakartridge

I recently saved up enough money to buy a drum e-kit, as I've wanted to play drums for a long time but never had the money for one, the closest would be one of those plastic drum kits for Rock Band (the one with the 4 pads and a pedal :P), but I bought an Alesis Nitro Max and it's super fun, especially bc I can hook it into my console/computer to play with Rock Band 3 (which is perfect bc it has a mode that adds cymbals to drum gameplay) and I can just spend hours drumming along to stuff, my end goal is to get good enough to where I can basically cover and play any song whatsoever with no guide or help needed.
My only complaint is that there's no easy way to do double bass, I know I can probably get a splitter or something but that would also require me to buy another kick tower, so idk