There is no particular camera or lens suited to capturing falling leaves and exactly what range and lighting you're in greatly influences what is possible.
If you want to try photography using a serious camera then I'd suggest looking at good used equipment dealers like ffordes.com (Scotland), lcegroup.co.uk (many UK locations) or mpb.com (online dealer). I've used all three myself and they rate their gear and you get various levels of warranty with whatever you buy. These, of course, are just the UK dealers I look at regularly.
A basic starter kit would be a used DSLR (too many to mention). If you're OK without movies you can get a used DSLR and 18-55 kit lens for as little as a £100 if you shop around and are patient.
Although they are not as flexible in terms of possible technique you can apply, superzoom bridge cameras can be very good as they offer a relatively small and simple way to get a very large zoom range (which is hard with large sensor cameras like a DSLR). Again look at used models.
It's against site rules to recommend specific products or services, so I'm already out on a limb, but don't get distracted by megapixel counts.