Hi, though this is my first post on this forum as a new member, I have been backing horses since a nipper, so I'm not talking without experience. Primarily I just wanted to say that you should really consider joining HRB, a lot of the work is done for you and the basic cost is a pittance compared to what you will gamble overall as a punter. (I've no connection to HRB only as a member)
As for speed ratings, I wouldn't give you tuppence for them as a method, but each to his own.
When a race is over, you have the most valuable piece of information of all. The Winner. There's a reason why it won, I would suggest to anyone starting out, that they should in effect backtrack, before you start spending time trying to pick a future winner, first spend time analyzing past races to a decent numeric sample without going overboard, if you've got basic Excel skills, you can rustle up a basic analytical spreadsheet, things will start to jump out at you.
The most valuable skill as mentioned up above, is experience and having an inate feel for a race overall, paying too much attention to jockeys and trainers stats, is for me, again each to his own, not important, horses win races.
Best of luck.