When I was at school I had a teacher who had a rather sadistic way of grading students. He started at 0 (everyone else's 100%). Then he took points off for incorrectness.
It's the same with a suit. The point is not so much to show off as it is not to eff it up. You start at 0 in the eyes of your interviewers and get points off for incorrectness. So go with something that will not get you points off. There's no need to get a 1 or a 2. You start at 0.
If you're applying for jobs, get a suit now, whether or not you get an interview. Spend as much as you can on it without breaking the bank. It will do you some good.
Applying for a job after finishing a Ph.D is about turning yourself inside out. You've been involved in the most introverted process you've ever done, and now you have to show yourself to the world at large. It's very painful, therefore. You feel so clumsy coming up with words to describe your project and you fear people's judgment.
So getting a suit will MASSIVELY help your psyche. It's a kind of commitment. Spending some money on the you who is going to get a job is essential. Same with the ikebana (see posts below). You are starting to learn to CURATE yourself. (More on this soon.)