Yeah, I had some issues getting a partner for my gerbil too.
I had read it was nice having them in couples, but when I went to the pet store they told me they could get some
but they could not guarantee any sex. Purely random. I could get a male and a female and end up with a ton of babies, and I would not know what to do about them.
So I chickened and bought just one gerbil.
Ah, yes, and the tiny tank they recommended me there...
When I was setting the tank I realized it was too small for one rodent, way too small, but I bought a nice second hand large fish tank. Also cheaper than the store bought one. That was easy to fix.
Figuring out his sex took much longer. Cause, you know, he needs to trust you quite a lot to allow you to check his thingies

When I knew he was a male I started searching for companions and was quite lucky to fund someone who had babies and was finding homes for them, so I got another one.
Had to split the cage to introduce them, but it was quite easier than I expected
It's lovely having them together.
Next week we'll be away a few days, so at least they won't be lonely.