I think you just started. At that point you should have two if not three good players(four and five stars) and 600 K and bit (more depending upon how many home games you have played) in the bank. During those time the price of young 5* players starts from 900 K and reaches up to 2 M so you won't have enough to buy those. If you are placed no 1 in the league and you think you can win the league with the current players I suggest you keep still till the end of the season and try to win as much as possible. Also raise the players quality as much as possible and try to make your 3* players to 4*. At the end of the season when you get promoted to to Level 2, your player's rating will remain same but the star will be decreased by 1.
After you got promoted to level 2 you should have some where around 2 M in the bank if you topped the league. Try to sell those 4* players which will be 3* by then. If you are able to sell them you would have enough to buy 1-2 good young players. If every thing goes to plan buy young 5* young players according to your needs, if things didn't go accordingly, you gotta have a strong squad to go far into CL rounds and Cup rounds(which is the real source of income during those stages) and if you think your squad is not good enough and you don't have enough money, I suggest you buy experienced or old school 5* players (age 28-30) which will serve as good as any for a season or two.
Always look for young free transfers. Always save some for building upgrades. Do not ignore the upgrades.

Best of luck