Depends on how much you shoot, and, how long you want to maintain the rifle. With the current import restrictions, you may want to get a deep & thorough spares inventory. The original G.I. stuff is dwindling fast, and lots of rewelded, commercial cast reproductions, Chinese, worn out, etcetera, parts are becoming, sadly, commonplace.

Keep in mind that a bad spare part is NO spare part.

First line (bare bones minimum):

• extractor
• extractor spring
• ejector & spring
• firing pin
• hammer
• hammer spring housing
• hammer & trigger pins
• trigger & sear
• bolt roller & retainer
• front sight screw
• flash suppressor nut
• flash suppressor set screw
• gas piston
• spindle valve spring
• spindle valve pin
• spindle valve
• connector lock
• connector lock pin
• op rod spring

Second line (preferred), and to include the items above as well:

• bolt complete (headspaced to your rifle)
• bolt stop, pin & spring
• elevation knob
• rear sight cover
• windage knob
• op rod guide & pin
• trigger guard
• hammer spring
• safety
• safety spring

Third line (deep support for the future), and this includes the 1st & 2nd lines above:

• op rod
• trigger housing
• trigger guard
• flash suppressor
• front band
• gas cylinder
• gas cylinder plug
• gas cylinder lock

Hope this helps!

Thanks again for the kind interest!