If you tap on the support under your turntable and hear do not hear resonance (sound through your speakers) the built-in suspension of your turntable mfg is sufficient.
I put my amps on Isocoustics aperta 200 supports and the sound changed noticeably.
A few years ago I had a Pro-Ject 9 and got a fair amount of resonance on the support I had it on. I could tap on the support and clearly hear my taps through my speakers. This was a 3K turntable. It sounded great, but the fact that the turntable was not engineered to absorb it’s own vibration was troubling. Swapped out for a Rega P6 and put it on the same shelf and there was zero resonance. Note that the difference between the two turntables is vast. One is designed to alleviate vibrations through weight, while the other is designed to alleviate vibrations via it's slightness.