Welcome to the forum. We are a friendly bunch and will do whatever we can to help you out. Don't be afraid to ask any questions no matter how simple you may think it is. Someone will have the answer.
I have a craftsman 12x36 with a QCGB for threading. I replaced the two 48 teeth idler gears with a 52/44 combo gear so I can do metric threads.
I think that I have every accessory in the craftsman catalog except for a taper attachment. Most tapered barrels will fit through the spindle bore. You don't really need to do that because your lathe is long enough to chamber between centers. I haven't done any barrels yet. Doing some barrels will be my next project. This is one way that you can chamber between centers.
Chamber reaming between centres (practicalmachinist.com)
This is what you will need to get full usage out of your lathe. You don't need to buy everything at once. Just buy what you need for the project at hand. Buy the best quality that you can afford.
A 3 jaw and a 4 jaw chuck. You can never have too many chucks. I have 3", 5" & 6" 3 jaw chucks and a 6" & two 8" 4 jaw chucks
Dead center for the headstock. The spindle has a MT3 taper. Live center for the tailstock. The tailstock has a MT2 taper.
A drill chuck for the tailstock.
Steady rest and follower rest.
At least 15 tool holders for your QCTP. You can never have too many tool holders. Tool holders can get expensive quickly. To save funds some of us have made norman style QCTP. That's what I did. My total cost for the tool post and enough material to make 20 tool holders was under $100. You can also make tool holders for your QCTP but you might need a mill to do that.
A spider for the outboard end of the spindle. I just finished making one. Not hard to do.
A boring head for tapering if you don't want to offset the tailstock. I made mine.
Collets. I have 3C collets and ER32 collets. I have never used the 3C collets that came with my lathe. ER32 collets are better because they don't block the spindle bore. You will need an MT2 adapter for the tailstock and an ER32 chuck for the spindle. I made mine.
Tool bits and boring bars. You mentioned carbide. You should consider using HSS tool bits. Forum member Mikey has a very long but excellent thread on grinding HSS tool bits in the beginner section. It is worth reading.
Micrometers, dial indicators with magnetic bases, calipers and inside telescoping gauges. A magnifying glass can be helpful at times.
A precision machinist level to level the bed of your lathe. This is an absolute must have to properly set up your lathe.
