I just started today, and I saw some video about the Rogue Flintlock Build (Is it correct?)
Mine is only releasing 1 bullet. How to make it to 4 or 5 bullets?
Just like the Video of this guide? (Hope someone can teach me)
[Build] Rogue - Flash Farmer
You must have multi attack legend affix on any of your gear or extra attack chance epic affix or from mythstones.
Thank you for the fast reply sir. It helped me alot. Thank you
The Zenith mythstone(2nd highest tier mythstone) can give you both(extra attack chances or multi attack) depending where you put it.
Or you can find gears with extra attack chance or multi attack.
Or you can gain extra attack chance through topaz and multi attack through ruby.
Actually there are lots of ways you can get those affixes.
Play and discover. 
Yes sir. Thank you very much for your help!
I’m not really an expert crafter. But glad I could help.