New to tattooing!!! Just want to know what the difference is between all of these! What does the numbers actually mean???

Sorry for the dumb question but I don’t know which ones to get, I got the 1003RL with my gun but it isn’t as thick as I hoped for, I have to go over the same line a couple times to thicken it up. Also with shaders I don’t even know where to start!

I’m doing mostly small tattoos everywhere, no big work or big designs.

Thanks for the help!!!