For starters you could 3* the third tier of mod challenges for pretty much any mod type. Resistance for speed set mods is pretty much the most important. Then Jawas for Critical Damage Sets and Scoundrels for Critical Chance are almost always second by importance. Once you've done that you begin farming them. You're going to look for Arrows with Primary stat Speed and everything else that has Secondary stat speed is a keeper.
Replies
Low speed for those, who don't remove TM.
High crit chance for TFP to land his tenacity down
Potency is less important after tenacity down has been applied.