If i am not a supporter...how could i see if one of my player is increaising his ratings on the skill that i`m training?

You have to manually track the skills being trained.

for that you can use the GI manager tool(dont know if its still around ) Or periodically record skills electronically

PS Oh well before I forget you can also use the good ol pencil and paper OR sharp rock and wall( I use the last one, Its a good workout and keeps the neighbors awake )

i still keep an updated record on with a pencil and paper even after getting suppporter its easier for me to check stuff on there