How fast are you intending to ride at night?

I'm by no means an expert (questionable for me to even offer advice), but for your budget I'd probably go with a 2 light set up. P-Rocket XP-G R5 for a thrower and Romisen RC-C8 II R2 can do double duty as flood and flash. Problem is that just those lights would run ~$64 shipped. You'd still need to get 18650 cells and charger. As for mounts, if on a really tight budget, use rubber bands or old bike inner tubes, hose clamps, or even duct tape.