There’s no actual “BEST” set, if there was, everyone would have the same build and it would be boring. There is however, good combinations of affixes, to form a custom set/build. Look around the guide section for specific builds, most of them explain how to use them and where to use them.
About the crafting part, there are some items that are very good as they are (Eternal Obsidian Daggers) but mostly, you’ll be doing a ton of crafting to get a good build, but the base items of some of these builds will require you to farm what we call “Rare Legends”, these are legends which has affixes that can’t be achieved from crafting. Perfect examples would be Vaccus Bow (Weapon Damage 100%), Mutiny (Elemental Damage 100%) Nadroji Items (Nadroji affix, Blind, Stun Immune, +2 Set) etc.
Hope this helps.
Cheers.