Start at 60 bpm (or as low as you need to, say, 40bpm) with quarters, then 8ths, then triplets, then 16ths, then triplets, then 8ths, then quarters, 1 measure each. Do this 4x. Now click up to 66.
When should I get a double bass pedal?
You'll need a double pedal to make it work. It also has a lot to do with mental coordination. When your feet are working double-time, it's difficult to make your hands independent. So, you're going to be limited to some basic double-bass songs if you're working with a single bass and single pedal.
How long does it take to get good at double bass?
To answer the question, when I decided to take my double bass playing seriously, it took me about 6 months to get to where I felt REALLY comfortable with it. BUT, I worked really hard at it. I worked through multiple books, spent alot of time playing with a metronome, and spent time mimicing my hands and feet.