First Big Sale

Last week I made my first big sale of a youth player, so jumped from about 500k credits to 12m credits. Since then, I have upgraded by training facilities a few times and bought a couple of better players for my squad.
But what's next? - since coming back I have been buying older players to try and help me get up the divisions a bit, is it time to start looking at players that won't decline so quickly? I'm a bit scared to spend large chunks of my credits when I haven't got anything coming in at all really. What's the best course of action for me?

get as high training as possible

sell the whole squad

prob easiest most pain free way

Transfer List everyone - hopefully for more than you paid for them, but as the cheapest available for their age & rating.
Replace them with better younger players as and when necessary, and transfer list them all too.
Trading players to make profits is the way ahead in this game