I tried a USB Hub that had on and off switches but it was a cheap one, It did not last long, after awhile no power going through it. If you get one, Do your research and pick one that has great reviews. It pretty much comes down to this, You get what you pay for.
If you are using a laptop then a powered usb3.0 hub (I recommend a 4 port one) can be useful since many laptop motherboards have difficulties supplying sufficient voltage under load. Just avoid plugging in additional devices into it, just your Rift is best. I used a pretty generic, but not cheap, powered hub from Amazon (think it was one of the Amazon Choice ones) when I used an Alienware 17r4 laptop and it helped a lot.
if you have a desktop pc a powered hub may be useful if your pc power supply is a little on the weak side (less than 550-600w). Otherwise a pcie usb3.0 card powered from your pc power supply is best imho. I have one of the top end Saitech (sp?) 4 port 4 channel cards on my current desktop pc and this works very well for me. Kinda expensive but I agree with OP that you get what you pay for.
what will be the best thing to buy my rift s keeps crashing i dont know if its my usb
Sorry, impossible to say since you do not include any PC specs or how/when your Rift S crashes, and any troubleshooting you've tried so far. You do not even mention if you have a laptop or desktop pc. Asking open ended questions without any detail is not going to get you very far imho.
I suggest you start a ticket with Oculus Support which will include your latest log files. At least this will let them review your system specs/performance and hopefully identify your problem.