Before you buy anything
A few things worth knowing first
Buy a bike that fits. Road cycling is more fit-sensitive than almost any other sport — a bike 2cm too large will be uncomfortable on rides longer than 30 minutes. If you're ordering online, use the manufacturer's size chart and measure your inseam. When in doubt between two sizes, go smaller: you can raise the saddle, but a frame that's too tall can't be made to fit.
Get bib shorts before your second ride, not after. Most beginners decide 'I'll see if I like it first' and discover the hard way why they matter. Your sit bones take time to toughen up, and a good chamois pad is the difference between wanting to ride again tomorrow and never wanting to sit on a bike again. The $35 pair from Amazon is fine. Just get some.
Don't start with clipless pedals. The classic beginner move is to buy clip-in shoes with the bike, clip in for the first time in a parking lot, forget how to unclip at a stop, and fall over in slow motion. Spend 2–4 weeks on flat pedals first. Get comfortable with the bike, the gears, the brakes. The efficiency gain from clipless is real — it just isn't going anywhere.