A little different for me, the basic 1.5, 2.0, 2.5 mm hex drivers. Ball screws are a no go. DON'T GET THEM!!! They are just for lazy people who don't want to unscrew it the proper way. The only instance where you would want it is for unscrewing a nitro engine from a motor mount and thats 2.5mm. (or you could just take off the head) Shock shaft pliers if you work on shocks a lot, otherwise pliers and a couple layers of shop towels does the job. Pliers you probably already have, philips and flat heads you probably already have also. Flush cutters are a must have but pretty cheap. But RC specific it would be

2.0 mm hex driver (MIP or Hudy)
2.5 mm hex driver (MIP or Hudy)
​​​​​​​1.5 mm hex driver (MIP or Hudy) (For mip they come in a set all 3)
Flush cutters (Tamiya is the best but way over priced) Just get the hakko or equivilant for under $10
5.5 and 7mm nut drivers (MIP or Hudy) (Also come in a set for MIP)
Turnbuckle wrench (non mip is fine, just get one with everything, the TLR one is good and the Kyosho one is good)

​​​​​​​You will end up getting other stuff later but the top 4 are must-haves.