The following is a collection of best-in-slot suggestions for the Crafting classes; they all share the same number of slots, stats and materia caps, so what applies for one generally applies for all (but perhaps not always).

Please read look at this excellent breakdown for the crafting materia caps and HQ gear statistics regarding the best vs most affordable way to cap your level 50 crafting class:

Disciples of the Land: Best Materia for Level 50 Crafting Gear

(excerpt from FFXIV Forums: Best Materia Setup for Crafters – by Raldo

Mainhand: Can't meld the best Lv50 mainhand tool. Go do your class quests, you lazy sod!

Offhand (HQ Militia): 19 Craftsmanship; 11 Control; 3 CP
- It is impossible to reach all the stat caps on this, so it's your pick what you meld.

Head (HQ AF): 4 Craftsmanship; 5 Control; 0 CP
- Optimum meld: Control III, Craftsmanship II, Control II

Body (HQ AF): 16 Craftsmanship; 5 Control; 0 CP
- Optimum meld option 1: Craftsmanship IV, Control III, Craftsmanship III, Craftsmanship III, Control II
- The above option has less reliance on Tier-4 materia
- Optimum meld option 2: Craftsmanship IV, Craftsmanship IV, Craftsmanship III, Control II, Craftsmanship I
- The above option has less expensive forbidden melds

Hands (HQ AF): 4 Craftsmanship; 5 Control; 0 CP
- Optimum meld: Control III, Craftsmanship II, Control II

Legs (HQ AF): 1 Craftsmanship; 5 Control; 3 CP
- Optimum meld: Control III, CP III, Control II, Craftsmanship I

Feet (HQ AF): 1 Craftsmanship; 5 Control; 3 CP
- Optimum meld: Control III, CP III, Control II, Craftsmanship I

Waist (HQ Raptorskin Mrch. Purse): 3 Craftsmanship; 5 Control; 3 CP
- Note: Since this is not iLvl55+, it doesn't accept tier4 materia.
- Optimum meld: Control III, CP III, Control II, Craftsmanship I

Neck (HQ Electrum Choker): 3 Craftsmanship; 3 Control; 5 CP
- Note: Since this is not iLvl55+, it doesn't accept tier4 materia.
- Optimum Meld: Control III, CP III, CP II, Craftsmanship I (your pick which tier-3 materia comes first)

Ears (HQ Red Coral Earrings): 3 Craftsmanship; 3 Control; 6 CP
- Note: Since this is not iLvl55+, it doesn't accept tier4 materia.
- Optimum Meld: Control III, CP III, CP III, Craftsmanship I (your pick which tier-3 materia comes first)

Wrists (HQ Militia): 4 Craftsmanship; 4 Control; 6 CP
- Optimum Meld: Control IV, CP III, CP III, Craftsmanship II
- Alternative Meld: Control IV, CP IV, Craftsmanship II, CP II
- I used the alternative meld since CP IV materia has literally no use except for this gear slot (or melds onto NQ gear), so it's generally cheaper than any other T4 crafting materia.

Rings (HQ Aetheryte Ring): 4 Craftsmanship; 4 Control; 3 CP
- Optimum Meld: Control IV, CP III, Craftsmanship II
- Alternative Meld: Control III, CP III, Craftsmanship II, Control I

NOTE: you should always upgrade and meld your neck/ears/wrist/rings/belt first, since they are shared across all of your crafting classes.