To better understand the sport, I can't really help, but if you ever have any questions you want to ask, feel free to post them, and I'm sure myself and a few others would be happy to help if we could.
As for sites, for me, the diary when I'm looking at historical information on horses, or looking to handicap a race, is equibase. You can get prior results, breeding lines, workout times, etc. for every horse in the country at any time. It has the cards and morning line odds for every race at every track, and then shortly after has the charts for each race. It's free for the most part, but there is a subscription fee for more information, although I don't use that. It also has lifetime and current stats on stables, owners and trainers too. For actual betting, I mostly use a private site, but I also go directly through TVG. There isn't a lot of value on TVG that you can't get from equibase other than the immediate odds going right up to race time, and live video of each race from most tracks.