$75-100 should get you what you need, easily. When it comes to noise gates, it's not the quality of the pedal, but how you use it. The difficulty with trying to clean up the sins of a high-gain pedal is that the user ends up expecting too much out of the noise gate.
Gates are intended to tell the difference between signal and "noise", based entirely on signal level. It can not tell the difference between what you intend to play, and what gets generated spontaneously by sources of noise around and in the guitar, cables, pedals, etc. So what you need to do is make that task as easy as possible for the gate.
If you stick the gate after a high-gain pedal, then whatever noise entered that pedal is amplified, and so is any hiss generated inside the pedal, making the difference between signal and noise smaller. So, what many smarter gates do these days is to include a loop, indicated by the presence of send and return/receive jacks (i.e., look for a gate with four jacks, and not two). Your guitar goes directly into the gate. The send jack goes out to whatever pedals you are going to use. The output of the pedals comes back to the gate, and then the gate goes to your amp. This allows the gate to tell the difference between wanted and unwanted signal at that point where it is easiest and most reliable to do so, but apply the gating at the end, where the most noise will have accumulated.
The final output of the gate does not have to be the last thing before your amp. If you have other pedals that are known to not contribute much noise at all, feel free to stick them after the gate. What is most critical is to clean up the amplified hiss/hum that your higher-gain pedal/s have produced.
