At the moment, I only have one cat of my own, although I need to accept that my long term foster isnt going anywhere - she has been here 11 months, and as I provide all the food and litter, plus paid for her dental that she is mine!! I normally have two (I only adopt oldies, and generally end up with one that costs a fortune, average vet bills for the last two years have been 4 figure sums, and that is mainly just on one cat!!), I lost one last November, and had a lot of long termers, so didnt feel the need for a second, and then when I did, i managed to pick one with cancer, so she only had 5 weeks here. My comfortable limit is 5, although it isn't good at the moment, having logistical issues!! I do normally end up with 6 though, although that is only possible when there are long term integrated cats.
i dont do kittens, i even let everyone else at the rescue have them, I have only had 4 lots in 4 years, I prefer to take in adults and oldies. I think male/female combinations are good, female/female can be tricky, and i haven't had many male fosters, so rare for me to have more than one male in the house, especially since i lost my male cat 2 years ago this month.