1= Square
2=Triangle
3=X
4= Circle
U= up
B=back
F=forward
D= down
So db4 is down back circle.
Here are my steps to get to a decent level fairly fast
In between each step is practice mode, memorize the characters combo strings and special moves is essential. Check out the character specific guides, don't be afraid to ask questions.
Step 1= Tutorial
Step 2= Arcade Ladder on Normal with every character
Step 3= Choose your favorite 1 or 2 characters
Step 4= beat arcade ladder on expert with both characters
Here are some basic tips
Down and 1, and down and 3 are generally your characters fastest moves. When some one is rushing you down use these to help get them off of you.
You can cancel your dash with block. This is very useful for getting around quickly and safely. Dash, and while you are in the middle of the animation hit block. You can repeat this very quickly, and you will learn to cancel thw dash at different distances for different situations.
You can link special moves off of normals and combo strings. What this means is with a character like Cyrax you can hit 12bb3 and you will do two punches followed by his net special move. The general idea is 2 hits linked into a special move, although certain strings and moves can not do this the majority can.
If you have any specific questions. You can think of just ask em here.