The first thing you need to do is learn to block. Go into Practice mode, set the AI to Very Hard and work on blocking their attacks. When you're done that, go into Practice mode, set the AI to Very Hard and work on blocking their attacks because you didn't spend enough time on your blocking practice. If you can get even half decent at blocking, the game instantly becomes ten times easier. Don't work on punishing, counter attacking or anything like that - just get better at blocking.
After that, take a straightforward character like Scorpion and work on a simple combo string. Something like B14 - MB Teleport - F34. Nothing long or flashy, just one string into an amplified special into another string. It is far better for you to lean on using a short and simple combo string which you can hit 80% of the time than a long and complex one that you can only hit 20% of the time. Once you can start doing it consistently, change the starter string and work on switching up high and low attacks into the same special and ender.
If you can get to a half decent level of execution on that stuff, then start searching out the training videos which talk about more advanced concepts and longer combo strings. Until you can do the basics, however, those aren't too much use.
