It depends on what you're after. Sometimes, less is more, and not every villain need be hyper-nuanced. Sometimes, being unapologetically selfish is a perfectly valid motive, however, I would try to make them human even if they're most definitely selfish.
While most ideological villains are the hero of their own story, consider their actions justified, plenty of villains ain't like that.
A good way to look at it is to observe everyday petty villainy from people. Sometimes there's a clear rationale behind it, sometimes people are just pricks. For example:
A low-income man has an ill daughter in a country that doesn't provide free-at-point-of-delivery healthcare. He therefore supplements his income by mugging richer people than himself. To him, he's definitely the hero; he's just doing whatever he can, the law be damned, to save his daughter.
Another low-income man has a wife that he regularly beats the crap out of, then sells her a patter about how he's sorry, and why'd she have to make him hit her, all that stuff, keeping a woman in a cycle of abuse because he wants a toy to take out his sadism/anger on. This guy probably knows on some level what he's doing is wrong, and just doesn't care.
The latter case could easily be a really simple villain; this guy, if he was high income, would probably be the sort to kill prostitutes with impunity and relish in the relative immunity from the law his class has.
Just remember that amid all the pressure writers have these days to make 'nuanced' characters that sometimes, people are unapologetic, selfish assholes.