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, "rebuilt", commercial cast reproductions, Korean, worn out, etcetera, parts are, sadly, becoming 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
• op rod spring
• gas cylinder lock screw (if you have the late one with valve)
• clip latch
• heavy duty clip latch spring

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

• bolt complete (headspaced to your rifle)
• bullet guide
• follower & slide assembly
• follower rod
• follower arm
• follower arm pin
• op rod catch
• elevation knob
• rear sight cover
• windage knob
• hammer spring
• safety
• clip ejector (safety spring)

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

• op rod (new if possible)
• trigger housing
• trigger guard
• gas cylinder (new if possible)
• gas cylinder lock (new style [high hump] recommended)

Hope this helps!

Thanks again for the kind interest!