dude you don't need to buy one. if you really want to improve your tempo... kung may keyboard ka dyan, kahit mumurahin may background samples mga yun. that is what i used nung medyo nagtra-transition na ako from keyboards to drums. i used to train to all the beats in my yamaha keyboard. dun na rin nag-improve natural metronome ko. tsaka if you really want it the easy way, go basic 1-2-3-4. ganon tinuro ko sa wife ko kasi nangingialam magdrums eh.
i reckon kelangan mo na talaga ang metronome kapag:
mayaman ka: syempre you can buy what you want
recording songs : para may systematic beat na sasabayan ang ibang instruments.
you cover off-beat(tama ba?) songs - the singkupado sh1t...
i'm a poor drummer who can't actually buy some fancy shmacy stuff but you know what helped me through? Improvisations. I see what stuff i can substitute for the real thing.