Brandon -

It's common to keep your attire business casual, but the key to proper dress code is based on the position you're applying/interviewing for. If it's a management role, dress to impress but if not, keep it business (appropriate) casual, and I wouldn't consider jeans as business casual. Definitely invest in (1 or 2) black/grey slacks.

Business casual clothes are the preferred ones even if it is a job that like its employees to wear jeans and t-shirt

Depends on position one is applying for. If seeking management level then wear to impress. If you're a tech/ nerd I would wear decent casual.