Yeah I usually play as a human. Mostly because I prefer the human portraits and bodies I've found in the art packs so far. I think purely based on stats I would be more likely to play as maybe a Dragonkin or a Drow but I don't like the art I've found for either of those races so far. I could just use art from another race instead I guess but have been too lazy to so far.Not sure if you are lucky or wether you play as a Human...
All Slaves I start with and can find are of different races, so they require atleast the breeding sow Job trait... and if they have that the stats of the offsprings are based on the mother.
So normally I try to get my assistant slave up a few Level to learn some Magic Job Traits and than make her a Breeding Sow in order to start some useful slaves... if I gather materials and Gold I'll try to Upgrade that assistant so that her offsprings have better stats from the get go
I guess that's actually a bit of a hidden advantage for humans that many might not think about though. Humans can breed with several of the other races without needing them to have the breed sow perk so having the main character's stats boosted guarantees that your kids will have good stats even if you breed with a slave that has stats that are mediocre.
The only reason I generally need to even visit the slave markets is to complete a servant quest in the first week or to buy a slave of a specific race later on if I want one. I get plenty of kids to never need to buy any slaves for the entire game, although I would still get Daisy. I actually don't buy any slaves from the slave market to keep unless I want a specific race.
So the method I mentioned works fine for any race, you just have to rely exclusively on kids from your initial slave if you don't go the breed sow route. I've played as Drow or Dragonkin before and just wind up with nothing but my own race for slaves with the exception of Daisy.