Well, for someone just starting out, I recommend doing what you've done here, and ask in this and other forums. Look in those forums and see if they have a subforum for new products (most do).
Finescale publishes a section on new products, too, including aftermarket sets of various kinds.
Do you have a modeling club near you? Visit it, then, and talk to the members. You'll get some good suggestions from them, too.
You'll get to recognize makers' names, then, too. Eduard is one manufacturer that has a pretty wide range of sets, for a lot of different makers' kits, and different subjects.
You can order from vendors like Squadron and Sprue Brothers, but also look to see whether a particular aftermarket maker sells its products through its website. You might get a better deal, than buying from a retailer. Shop around, too. Amazon.com might be useful, too.
eBay is another place to look. I would search by the subject you're building, first, and then weed out results as you go.
Hope that helps!
Best regards,
Brad