Make sure the players you want to keep have contracts or their contracts will end.

Save up tokens and start bidding in new season. (Avoid bidding wars)

Try to sign 5 star players ending in 4 or 9 Quality.
- look for players aged between 18 - 22 although the occasional 25 year old is ok if they're worth it.
- my preference I aim for players with multiple positions like DR/DMR, DC/DMC, ML/AML for example.

Finally, accumulate green packs and train 18 year fast trainers (usually the highest value)

I hope this helps