For the 89 bucks you are going to spend on a MA957 (which includes, bubble counter, needle valve, regulator, and nylon washer) you will probably end up spending more if you buy it piece by piece.
You can do a DIY reactor though if you really want to save a buck. You can also do a DIY drop checker with DIY 4dkh solution.
IMO, the MA957 is the way to go on a budget. I've been running one for 1.5+ years with no problems.