I just let my son have as much as he wanted from day 1. Unless it gets ridiculous regulating their own appetite is part of this process.
I tended to offer water alongside food but do solids inbetween breastfeeds which also helped to gradually space out the breastfeeds (my son was a bit of a milk monster.) I think the risk with doing solids at the same time as a breastfeed is due can result in it being refused completely. Although solids will gradually reduce the milk intake it does need to be a gradual process. I also found by doing this, for the first time ever we ended up with some kind of routine that did work. My son was very resistant to being fed only on waking and we did a lot of extra feeds. I realised much later that my son is just a hungry boy. He will eat loads of solids now and drink milk all day if I let him.
Well done for keeping breastfeeding.