Don't get discouraged. You have to remember that on most dating sites, men far outnumber women, and women (especially the very attractive ones) probably get messages from men every single day - not to mention being frequently hit on in their everyday lives. With that said, no matter how clever and smooth your messages are, and no matter how great of a guy you are, you're probably not going to get a huge rate of response.
Regarding those dating "courses" - ignore them, especially if they're charging you money. For one thing, you've got to have a certain type of personality to even benefit from them. If you do have that "pick-up artist" personality and that's your thing, then I'd recommend searching the Internet for the exact same information at a low cost of... free.
How exactly do you define "success"? Meeting someone for a date? Finding true love? Having sex? Personally, I've met a few people from online, but ironically, none of them through a dating site. I think the extent of your success will be based largely on how you come across, what type of person you're looking for, and what type of encounter you're looking for. Then, choose a service that matches your preferences. I'm a fan of
OKCupid, because it's creative, accurate, and free.
Let us know how you're doing!