One thing I'd like to know before I quit and sell all my fighting games/controllers/guides. How long did it take some of you to get to the point that you considered yourself "good"? How long did you have to practice? And did you have fun doing it? What motivated you to keep going?
Main thing that will help is having some people to play offline and level up with.
I'd suggest starting off with a very accessible character like Ryu or any of the shotos.
Don't worry about fancy combos at all when you're starting off. Knowing your characters normal moves are key to mastering a SF game. Knowing your normal's frame data, hit/hurt boxes, range, priority and juggle properties will do a lot more for you in the long run then practicing a fancy combo in training mode. Once you go to a real match, you'll just be focused on that combo and won't understand how to actually setup the combo.
The main SF series and SFxT are heavily focused on footsies. This is where the normal move knowledge will reign supreme. In SFxT for example, all of Ryu's crouching normals are special move cancelable...even his cr.HK.
If you have the guide, all the info you'll need is in there. If you don't, I'd recommend going into training mode choose to fight against Ryu and record the dummy performing a cr.MK. This is very good poke for Ryu and you'll want to know what beats it. Then with the dummy in playback try your normals and see what beats it. If you can shut someone down from a footsies game, you'll win. Period.
Repeat this with other characters and often used pokes. Once you're comfortable with your normals, go play some matches only using normals so you can get a feel for them. Their priority, what juggles etc. You're looking to get a really good fundamental feel for how the normals work in game.
After you can do well with normals watch videos, read guides etc and pick ONE easy combo. I can't stress this enough, don't try to learn everything at once. Pick something VERY easy like Ryu's cr.mk > hado. This is about as easy as it gets and it's quite good. With your knowledge of how to actually land your normals in a real match, try using cr.mk > hado in some real matches. Only that combo and other normals. You'll want the basic bread and butter combos to be second nature when you play. If you're ever consciously thinking about normals and BnBs, you're not ready for more advance tactics.
tl;dr. Focus on the basics. Normal moves and one or two very easy combos. Once these things are second nature, THEN worry about the rest.