You might ask the tour organizers for suggestions on what to bring. You don't have to have fancy clothes per se, just things that serve their function or multiple functions. You'll likely want to buy some things that are versatile and that help you go from a chilly morning to a warmer afternoon without too much effort. For instance, a wind/rain jacket with detachable sleeves, arm warmers, leg warmers, toe covers, knickers, maybe a bolero. I'm not sure if your running pants are tights or just workout pants, but you'll probably want to invest in a pair of unpadded tights. It wouldn't hurt to have some kind of headcovering for both cold and rain and longfinger gloves. And unless you want to do laundry every night, you should have a few pairs of relatively new shorts, some jerseys (both long and shortsleeve) and a couple pairs of short-fingered gloves.
You might finds some deals on eBay. Otherwise, check for sales at online stores like REI, Sierra Trading Post, Campmor, Nashbar and Performance. Whatever else you buy cheap, don't scrimp on shorts. You're going to be spending some serious time in the saddle and it will not do to have cheap shorts.
Live with intention. Walk to the edge. Listen hard. Practice wellness. Play with abandon. Laugh. Choose with no regret. Continue to learn. Appreciate your friends. Do what you love. Live as if this is all there is.
--Mary Anne Radmacher