Booster pump AFTER filter. This helps protect the pump and makes it last longer.
Also it's the RO that needs pressurising not the filter, hence pump goes before the RO.
TAP~~FILTER~~BOOSTER~~RO~~DI
Flush for 10 mins daily before you fill up, when ready to fill close the waste valve all the way to pressurise the system, then open up slightly so the waste is set at about 3/4.
You'll get more pure if you keep the waste fully closed but it will kill your membrane quickly. The more you open the waste valve the less pure you get but the longer the membrane lasts.