Its extremely rare that I will ban a class outright, or a specific race. In general base classes is my prefered method to add options to the game. I'd much rather use a new base class to represent a player's concept then a new feat tree or even an archetype. The only class I've banned that paizo has released is the arcanist. And that is mostly because I have very strong feelings against the whole spontaneous prepared casting thing, and I'd prefer not to go down that road. The summoner I allow, but I require some deliberat non-optimization since in general eidolons just come out super optimized because of their heavy custimization.
In terms of races, I happen to really like weird races in my games. Other then things clearly not meant to be player races (no quickling characters) I generally allow most races. I dont however allow evil characters. But I'm fine with the drizz't school of CG child of an evil race rebelling against the evils of their parents trope. So if you want to play a goblin, or drow, sure, lets go for it. I think the weird fish out of water races can make for some really interesting moments. And they represent relatively less tread territory. I've run games for tons of elves, humans, halflings, and dwarves. But a wayang, grippli and changeling in the party? Thats new territory roleplay wise.
The thing I do require is that all players come to me with non-core options besides base classes they want to use, and I reserve the right to line item veto if I think it is going to be a problem.