Cycle clothing is extremely advanced these days, but also very expensive too. My best advice is to focus on two key garments:
The first of these would be a good pair of shorts. They are the only thing between you and your saddle, and bearing in mind which bit of you comes into contact with the saddle, it’s worth spending cash on them! Unfortunately club and team kit is often made with the standard male cut chamois, which doesn’t suit most females. An incorrectly shaped chamois can leave you with some serious abrasions on the inner thighs and bottom
Find a brand that suits you and stick to it. The cycle clothing market has, until very recently, been directly primarily at men- not overly helpful for us girls! There are a few manufacturers now producing female specific kit so it’s worth investigating.
The second piece of kit worth investing in is a good sports bra. Road cycling is not high impact but it does put your upper body in an inclined position for prolonged periods of time; your breasts need support in this position to prevent unnecessary stretching of delicate ‘suspensory’ ligaments, which help the breasts to keep their shape.
The correct bra will support the breasts and reduce movement, therefore restricting stretch of the ligaments and subsequent sagging. The benefits do not stop there however; if you have larger breasts then the correct sports bra can prevent painful movement as well as neck and shoulder discomfort. Riding with a normal bra would be like riding without a chamois in your shorts!
You need a sports bra with moisture-wicking fabrics, which dry out quickly. Again, find a bra that suits you and stick with it.
Remember, neither of these two garments should be new for the event. You should try new clothing for short periods of time initially and build up gradually