I agree with others about kits -- they're far and away the easiest way to get started, since they (theoretically) contain all you need, and the lists of [carl sagan voice]billions and billions[/carl sagan voice] of minor variant chemicals at B&H or the like can be confusing. (Sometimes adding stop bath or final rinse/stabilizer to a kit is useful or necessary, though. Stop bath you've probably got, but if a C-41 kit doesn't mention it, add some final rinse for newer films or stabilizer for older films to your order. If in doubt, use stabilizer, but be aware that it contains formaldehyde, so treat it appropriately.) Unfortunately, kits are often pricier than buying individual components, and AFAIK neither Kodak nor Fuji makes C-41 kits any more, at least not sized for home darkroom use. This means you may need to use third-party chemistry if you go for a kit. Third-party C-41 kits usually (always?) use a blix rather than separate bleach and fixer, which is a disadvantage.
Alternatively, try calling a retailer rather than placing an order via the Web. That way you'll be able to discuss your needs with a salesperson who should be familiar with the specific products the retailer stocks. If you're ordering by Web, Freestyle and Adorama have less confusing lists of color chemicals than B&H or Unique Photo. Of course, the downside is that the less confusing product lists are also less complete, but they've got the things a home darkroom user would need.
More broadly, for C-41 you need C-41 developer, optionally a stop bath, either a blix or separate bleach and fixer, and either final rinse or stabilizer. Separate bleach and fixer are superior to a blix, in my experience.
For RA-4 you need RA-4 developer, optionally a stop bath, and an RA-4 blix. Most kits have just the developer and blix.
For both C-41 and RA-4, developers and blixes are often shipped in multiple bottles; you mix them together at time of use. If an ad mentions "part A" or "part B", be sure you get all the parts. Some third-party products ship single-part concentrates rather than using multiple bottles. This is more convenient, but I suspect that shelf life suffers.