Where to find good mods with high speed secondaries

if you're getting low dot mods from events, it means you're doing low level versions. (better to sell the 3 dot mods for more credits)

The most you can see on a level one mod is 5 speed. At levels 3, 6, 9, and 12, a mod will gain a stat. once a mod has 4 secondaries, it'll start upgrading those stats. So gold mods will start leveling up stats at level 3, but a blue mod won't start until level 9.

After that, its all luck. If a mod doesn't proc speed, stop leveling or slicing it, sell it and move on.