Read this post. And then check out the rest of my posts tagged “Tuxedo”.
Price including shirt and shoes might go north of your budget though. Start sniping eBay for those, if you can. Also, remember to set aside money for alterations. Upside is that a decent pair of black captoe oxfords can be worn with other suits (for interviews, weddings, church, funerals, etc.) — and you can probably find a pair of Allen Edmonds Park Avenues for around $100 if you look long enough on eBay. Bowties can be hand for cheap via The Tie Bar.