dSkill 50-54: Mythril File (i40) [77% - 83.6%] (buy the mythril ingots from the Amal'ja vendor) {probably better choices here}
dSkill 54-64: Horned Hatchet (i49) [60% - 77.5%] (1x FC1, push this as far as you can)
Horned Hatched is actually i48, like the other recipes above it (the recipe levels are irrelevant to the item level)

I prefered making Bas-Relief Cobalt Saws (top of the 46-50 recipes in BSM) as they required only 3 mats, none are leather or sinews (expensive and annoying to farm up) and started at 50 and made it all the way to 64 with 150 of them.

Lots of FC1 and FC1x2 from those Saws.