its case by case but it sounds like your really unfamiliar with the garand. its just best for your first one to be in good working condition. once you learn its ins and outs then build one
not saying you cant just jump right in just dont expect to save money if you do it cold feet.
the tool you will get the most out of is a bolt disassembly/reassembly tool i highly recomend the strobel m1 m14 carbine bolt tool. it works really well on all three bolts.
another must have is the gas cylinder combo tool and gas cylinder plug valve fixture the valve tool really helps cleaning but not reallllly needed less you shoot a LOT. the combo tool serves as a means to steady the barrel while adjusting the front sight, has a screwdriver end for removing the gas plug and serves as a wrench for removing the cylinder itself.
a .30 cal muzzle gage is a MUST have if your shopping for a garand M1a or m1 carbine in gunstores or gunshows. avoid counterbored rifles unless the rest of the gun is in very good condition and you plan on rebarreling or just want a plinker and get a smoking good price. counterbored barrels were shot out and then the first section of rifling removed. always assume counterbores have excessive throat erosion unless you invest in a throat gage. because any schmuck with a power drill can counter-bore i would personally not fire a counter-bored rifle barrel of unknown origin regardless of what the seller says. you see this a LOT at gunshows and pawnshops. the military did counter bore barrels as a field expedient measure during wartime. they also did it for training rifles but they also re-throated the barrels. joe shmoe with the power drill didnt re-throat and there is no way to tell and no way to tell if it was bored correctly.
a poor man's bore gauge is a dummy round with a real .308 bullet set to the proper OAL drop the point in the muzzle if the brass hits the muzzel its a worn barrel.
if you plan building:
bolt timing gauge
gas cylinder gauge
i list those as optional because unless your sorting through spare parts or building from scratch with unknown parts you dont really need em. they all list for over 100$ each for milspec versions. the cost of those tools are why you wont save money unless you plan on building and selling garands to make money.