I started out with a Milwaukee regulator, which includes a needle valve, bubble counter and solenoid valve. It did the job, but is so cheap it kept letting me know I didn't pay much for it. There are a few other cheap brands like that, all priced about the same, $80 to $100. Or, you can sometimes find a used one of those on ebay or craigslist, for a much lower price. If you don't feel confident about screwing all of the parts together, so they won't leak, one of those cheap regulator assemblies is a good option.