Exclusive pumper! Need help with supplementing!

What's the best formula for a baby that has never had any before? (He get a little gassy when I have dairy) Iwas an over supplier but the last two weeks I've been extremely stressed with moving from California to Florida so my supply tanked. While I try to get my supply back I'd like to give my LO formula while I bank my milk in the fridge for a couple days, any suggestions or advice?!