It took me one season on the Extreme Level to get promoted. Just buy players as soon as you have the chance. Pull up their loans a bit and they will join your club. Don't worry to loose money because of the high wages. Just make sure you end first in the third division, have the top goalscorer and the top assister, and win the tiny cup. You will earn a lot of money doing that, and there won't be any problems.
Go for Chilavert (Paraguay), Dida (Brazil), Kiraly (Hungary), Quintana (Colombia), Gamarra (Paraguay), Suarez (Mexico), Mokoena (South-Africa), West (Nigeria), Ulises (Ecuador), Novak (Slovakia), Gedic (Slovakia), Fadiga (Senegal), Denilson (Brazil), Mostovoi (Russia), Juninho Paulista (Brazil), Balakov (Bulgaria), Zahovic (Slovenie), Djorkaeff (France), Zuma (South-Africa), Olisadebe (Poland), Diouf (Senegal), Rebrov (Ukraine), Masinga (South-Africa), McCarthy (South-Africa), Emile Mpenza (Belgium)
Later you will be able to sell those players and get a lot of money for them. This gives you the opportunity to buy your favorite player(s).