breastfeeding advice

I'm 18 wks along with my third child. I had my older two children super young over a decade ago. Tried breastfeeding them but didn't have any encouragement or support or tips to do so. One had colic and they both had super sensitive tummies even though they were the sweetest babies. I really would like to breastfeed this baby for the first year this time exclusively. I need some pros to give me best foods to eat to produce enough milk and foods to avoid for sensitive tummies (since that seems to be a pattern. ) thanks!