If I'm pedaling more than 2 miles, I wear cycling kit. The clothing is more wicking, and keeps my work clothes clean/dry. I am lucky that my commute now is only 1 mile, so I never have to wear a kit, but I used to commute 10-15 miles, and I always wore cycling bibs. I can't imagine riding 10-15 miles without a chamois, no way! But, I also train/ride another 15 hours a week, so my sit bones could not deal with being sore from a 6 hour ride and then sitting on a saddle for a commute in jeans. ouch.
You don't need anything expensive or complicated, but it needs to fit correctly. Too big, and there will be chafing, too small and you will feel constricted. I like bibs, because I hate waistbands (who doesn't??) and they should be tighter than you *think* you want them, because they will stretch out. You don't need any special jersey/shirt, just a wicking running/hiking shirt will do. If you get a proper pair of cycling bibs, then you can wear baggy hiking shorts/running shorts over them, and a regular wicking shirt, and your sit bones will thank you for the chamois, and you won't feel conspicuous and super "kitted out"