I did some researching and found this really helpful site. I took a monet to copy and paste what I feels answers your question and have listed there link if you want to read more.
Can I eat with braces?
Yes! You can eat most of the good things that you can eat now. The only issue is that your mouth will be sore after you first get braces, so for the first week or so you may only want to eat softer foods. However, after that you should be able to eat normally.
How about chewing gum with braces?
Gum usually is not recommended. It can get caught on braces and pull them off. In addition, the sugar in the gum can get around behind the braces and cause cavities.
In some cases, it may be possible for you to chew a sugar free, non stick gum such as Freedent® or Wrigley’s Extra®. However, Freedent® and Wrigley’s Extra® will still damage some kinds of braces
Is there anything else that I can’t eat?
You probably should not eat hard sticky, gooey or crunchy foods. Caramel, taffy, peanut brittle can stick on your braces and pull the braces off your teeth. You also need to be careful with crunchy foods like carrots and apples and hard rolls so that you do not knock your braces off your teeth.
As for best painkillers I like Advil or Alive but if by any chance you are minor remember to ask first before taking any over the counter pain killers. I hope this has help you.