Depends where you live or intend to ride. And how fit you are I guess.
I got a double (first road bike) and was fine on the local loop with steep but short hills, even over-took some mtb'rs going up.
Soon as I went up on the (Yorkshire) moors…
Double means short cage derailler short chain double front shifter? So I swopped the 11-25t for an 11-32 SLX cassette, XT rear mech & new chain (CRC flood sale). Been up 25% no probs since. Also seem to use the inner ring a lot less generally.
Think it would have been cheaper to have bought a triple.