try search google: "dexcom free trial" 10 day free
alongside after "abbot libre free trial" 15 days free
thats 25 days there almost a month
There maybe other CGM's out there that also offer a free trial, just go with whichever app+ sensor you feel works for you after run out of free trials. u could also do some pringer pricks to see which is more accurate for yourself based then on accuracy price/performance get whatever works for you.