I think it all depends on their appetite. With my LO, I started out with lunch first, because this was the time when she was most receptive, awake, and interested. I think that once they are at 6 Tbsp to introduce another one. You don't want them over-eating so that's a good way to balance it out. My LO is currently eating 3 meals a day on most days, and started solids at 5 1/2 months. Some days she's less interested in certain meals, but in general she likes her solids.
I've heard that it is okay to introduce meats from 6 months on, some are doing this to get a source of iron if LOs are not getting rice cereal.