Mono and Rytm probably ain’t the best choice for dub music. It’s such an organic style, which is very hard to imitate with synthesizers.
If you want to continue down that road, a few pedals that might suit the bill are the Strymon El Capistan delay and the Vermona Retroverb Lancet (a spring reverb with a nice analog filter). Or if you want to go vintage, buying a real tape echo would work of course.
The best bet is to get a real drum kit and a bass guitar though…