Easiest ways to get Legendaries in Borderlands Pre Sequel

If you have no legendaries, you can try farming Iwajira. He has a relatively high drop rate for a legendary rocket launcher which you can use in the grinder. Just remember to always use moonstones when you grind them, or you may get a purple gun back.

Legendaries appear in the vendor at a much higher rate than BL2 - I got three at Level 15 alone. Legendary drops from random enemies are probably as low as they were in BL2...like way low. IF you know what boss drops the one you are looking for AND that boss respawns (many in the TPS do not), then you can farm him/her/it. I wouldn't waste money trying for getting a legendary from the slots -- again, very low odds it they are same as BL2 -- use that money to buy one from a vendor when it appears. It will.