Firstly,all formulae are more or less the same,choose any brand,but ONLY if lactation is insufficient. Use a katori and spoon to give top milk feeds,not a bottle. Secondly,contrary to common belief,babies do NOT produce so called "gas". It's swallowed air,during feeds and while crying. Also,it's normal for babies to have colic,specially in evening and night time till 3-4 months of age. What you need to do is give feeds at regular gaps of atleast 3 hours,burp him for 10 mins after every feed,do the same for colic and the so called gas,no medicine is required.