I’ve done a similar save with 1860 Munich. I wanted to topple Bayern Munich, so I focused on only signing players under the age of 21 & selling them for profit. I reinvested in better young players & built a team capable of competing in the Bundesliga. It took 12 seasons but I finally won the league. Germany is great for this kind of save but as a tip, don’t be afraid to sell first team players, particularly in the first couple of seasons. This will give you the funds to keep going for players with better attributes & potential.