To Start Food or Not To Start Food

So the little man is 4 months and 2 weeks.  At his 4 month check up his doctor gave the green light to start him on food when we felt his was ready.  Well how do you know when he's ready?  I know for the past week or so he's been waking up in the middle of the night wanting to eat.  I know my supply has gone down and we have gone from just breastmilk to almost all formula.  If we are going to start him on food what do we start with?  It is so confusing!  I've read so many different opinions.  Rice cereal, right to bananas (which I have to say I find personally disgusting!) or avocado or sweet potatoes.  I know that I want to make our own baby food but I just have no idea where to start!