You can get a male. Many people have had two unneutered males together. There may be a higher chance of problems, but it's definitely possible. It's not guaranteed the glider you get will get along with your male regardless of gender. Females, I personally think are the easiest, but that's only when breeding isn't involved. I would recommend neutering your male no matter what gender friend you get him.
Neutering can help with dominance and territorial problems. That's not guaranteed, but it is a huge possibility.
It make a huge difference when it comes to smell!
Most importantly breeding is a pain and it's potentially dangerous. They can have one to two joeys every six months. If you get a female the father might try and breed with her when she's older, unless you separate or neuter the father. If you get a male he might fight with the father when he's older and mate with his mother. If you don't neuter or separate than you will have a problems with incest.
It's difficult managing multiple cages. After a while they will stop getting along and you'll only be able to socialize one cage at a time (Happened to me at least). It gets over whelming fast.
If you are anything like me, it'll be impossible to sell any. You'll get attached. On top of that there are already many homeless and neglect gliders out there. Do you want to add to that?
Mating can be dangerous for the female especially if it gets rough. You must be prepared for the chance of injuries.
The female will need extra protein and nutrients. Some diets will have special instructions for the mother who is carrying joeys. If conditions aren't properly met the mother may reject or eat her baby.
Once you do the whole introduction process, and they get along, the female will be able to live with the male for the rest of their lives. Separation would only be necessary if they aren't getting along, an injury happened, or if the male isn't neutered and you need to prevent further breeding while you get your male neutered.
What do you mean buy more to keep from inbreeding? Sorry I just don't understand that question.
My brother had two females and ran out and got a free male. Bell, Rose, and Jack. Once they had Finn I was the one who got them. Through complications I now have two cages. One I take care of and one my sister takes care of. I have Bell, Finn, Quinn, and Ty (RIP). Sis has Rose, Jack (RIP), Aang, Kiwii, and Tiny. This all happened in a year and a half. All of them except the two who passed away are neutered. I had territorial problems, mating problems, dominance problems, all of the problems and stresses wouldn't have happened if we got Jack neutered.
Maybe do a bit more research and plan a head before breeding. Find a vet and a place to neuter. Even if you don't need it now, it's good to know your options before they are needed. Just a thought :)