Best way to improve a team?

[MichaelChris]

Hello, I'd like to know what is in your opinion the best way to improve a team.. I am fairly new to the game and this is how my team looks like:


As you can see I play with a 3-1-2-2-2 and I have an avg age of 23. My team has an avarage quality of 18 with Gerrard being the best player at 24*.
Now I would like to know if you think I should change my formation or keep it this way and what the best way to make my team better is; should I train only 1 or 2 players with rests or should I keep training the whole team?
Thanks in advance.